Wow he's 21?! What a crazy, controlling bitch! I could understand if he was a teenager, but damn.
If I were you, I would seriously talk to her personally about her behavior. I wouldn't let it ruin your relationship with him, though.

I have too! And that broke us up. But the best for you is to leave such a relationship. If she is like this now, before you got married, it will be worse after marriage! And obviously your BF doesn't seem to be able to get out of her clutch!

In my relationship, MY mom is the problem.  Even before we had dated a full year she expected him to be at all major family functions and holidays - even though he lives 120 from my parents and has his own family who would like him to be with them on holidays.  I can understand his struggles, and how he is probably trying to not hurt his mom but also carry on an adult relationship.  My mom has made me feel like a whore for sleeping with my boyfriend, and she claims I am "keeping him away from" her, which I was not, but I was simply trying to keep things fair.  She clearly tries to control me and my life and it has been difficult.  I just have to keep resisting, resisting, resisting, and hope that my SO doesn't run for the hills one day.

The fact that your SO is still hanging out with you is a GOOD sign...it means he is somewhat defying his controlling mother.  He probably hasn't moved out for many reasons, whether he knows he will have to struggle to pay rent, or maybe it's just easier to have someone cook and clean for him.  She might also become angry whenever he brings up the subject - I'm 23 and, while living in a different state for graduate school, my parents still consider me not moved out yet.  I can only say try to support his struggle for independence, and maybe try to have lunch outside of the home with him and his mom together?  It might also have nothing to do with you per se, but any girl that is "taking away" her "baby"!

21 years old or not, her house, her rules.  If he don't want to listen to it, move out.  It's simple as that.

In the time being, it's her house that he's living in.  Respect her wishes (even if they seem unreasonable).  Whenever he moves out and get a place of his own, he can do whatever he wants and his mother will not have any say in it.  Until then, you can continue sneaking into the house or find someone else.

my ex boyfriend  mother did the same thing he Was crotral his Life too . she got in fight with me and he told her dump me on the phone one Night and we Have spoken since then i found he see some one and it not great guy be around 

He's 21 years old. Where he puts his penis is none of his mother's business. He needs to explain that to her. And probably get his own place, too.

she is probably worried that you have an accidental pregnancy, then she has to help foot the bill or he doesn't have his life in order, so a relationship is distracting him from getting back on track to become independent. as mean as she seems, I don't think she is trying to run your relationship but thinks him cutting the cord is for his own good because it seems like nothing has changed for about a year.

I'm honestly going to side with his mother on this one. If he's living at home, under her roof, without helping or contributing to the household... then he needs to follow her rules. I can understand how judgemental parents can be about things like sex, and maybe she had better intentions for her son. I honestly can't believe that she liked you THAT much if she was willing to hate you over such a small thing. I would suggest talking to her yourself, asking what makes her so upset about the sex issue, and why she hates you now. That's the mature way of going about it, instead of making your boyfriend feel as though he needs to cut ties with his mother. She's his mother, and I would hope that he would put her before you most of the time, because family should come first, unless you're married and then their family is your family too.
There has to be a way this can be solved, but make sure you are following her rules. The fact that you are now sneaking behind her back makes you look even more untrustworthy, in my opinion. Why would you still continue going to her house... why would you not invite him to a place where it's neutral, or even over to your house? It just makes me think that there's more to the situation then you're really telling.

@jeezshoua@xanga - I agree, except with the part where sneaking into the house is acceptable.  It's trespassing, and I'd have you arrested, or at the very least escorted off the property.
OP: Obviously, his mom is nuts.  But you have to respect her, no matter what.  I have this problem in my marriage: it's not his mother, it's practically everyone else.  His sisters are bitches, and his dad sexually harassed me on a number of occasions, in front of my husband (who said nothing) and once came very close to convincing me to commit suicide.  Now, my husband is by no means stupid, but for some reason he's blinded to the true nature of these people.  He thinks they have good intentions, and only want what's best for him.  Like your boyfriend's mother, they want to control his life.  They don't care if he's happy or not, they care if they're happy.  And they won't be happy with me in my husband's life.  Like your situation, the tables turned very quickly, but not because we were having sex.  We've been fighting lately, and my husband turned to his family for support.  They don't seem to realize though, that there's 2 sides to every story, and not everything he says is exactly true.  They're also filling his head with lies about me, because they are apparently smarter than my doctors and therapists and are capable of diagnosing me and giving him and expected outcome (I have mental illness).  For whatever reason, my husband buys into their bullshit.  If your boyfriend does, eventually things won't work out between you two.  You can't ask him to cut ties with his family, but you have to be able to convince him that you're not the bad guy, without saying that his mom is.  Respect her rules, and be super nice.  If you have to, avoid family functions.  As much as I'd like to tell you to tell them they're not welcome in your home, if you and your boyfriend ever move in together, it's not realistic.  It's his home too.  If they were friends, and they'd wronged you, you could say this, but not with his family.
Good luck.

@Covergirl_For_Sanity_Fair@xanga - I never said that "sneaking inside the house" was acceptable.  Obviously, she is doing that and if she wants to stick with the dude, she will continue to do that regardless.  I was only adding on to what she was already doing; not telling her that she should do it. 

@drunkdevotchkababy@xanga - I'd agree with you, but your reaction implies that he deserves no human respect. Whether she likes it or not, he's his own person. I could understand saying, "No sex in my house", "She can't be over here", but she has absolutely no right to try to control a situation that should consist of his own decisions outside of her walls. Her house, her rules, yes. But only when those rules apply to her house.

Man! I didn't realize he was twenty one when I started reading this. His mom's crazy, he's old enough to make his own decisions.