I'm going to take a wild guess and say that you lost your virginity in the missionary position, based simply on the fact that most people I know lost it this way. Especially girls.
But since then, I hope you've experimented with different positions. You hated some, thought others were so-so... and then you found one that you absolutely loved. One that hit the perfect spot and that you wanted every time, to your lover's not-quite-dis-pleasure.
Mine used to be what is known as the fox. It's basically missionary, except the girl has her legs raised up to her ears.
Lately, however, the fox isn't doing the trick. In fact, it's slightly painful. Probably because I'm with a different guy, but I lament the loss of my favorite position, and I can't seem to find another one I really like. They all feel OK, but none feel absolutely great.
Partly so that I can find a new position to try, and partly because I'm just curious - what is your favorite sex position?