If you're a virgin and you haven't yet had sex, then you can't really have a true sense of whether you're impotent or not.
Being impotent usually means not being able to get or sustain an erection - which is clearly not the case with you.
Erections come in all shapes and sizes, my husband's curves sideways, so I wouldn't be worried if I were you.
Porn is not the real world. Those guys are chosen because they are huge and because they can sustain erections for looong periods of time.