You have to have good sex to know for sure...imo.

If you haven't had an orgasm or been completely excited before sex then it won't be good, and if it's your first times then it gives you a bad idea of how sex is supposed to be.

Taking your time for the right person is a good thing. When the right person comes along then sex will be good, you'll be ready and willing and if he cares he WILL make it about you and not so much about himself. Sex is supposed to be about pleasing one another and not yourselves...men can sometimes forget that...but we forgive them.