Re: from a woman-question about being on top
He's probably bumping your cervix, which is very uncomfortable for most women. Make sure you're fully aroused and well lubricated before even considering intercourse. Then, try changing the angle a bit; lean forward or back, and see if that helps.
As for feeling incredible, well, because you can control the pressure and angle, and get plenty of clitoral stimulation from his pubic bone, many women find it easiest to come when on top. However, it's probably my least favorite position, lol. Everyone's different :-)