I didnt bleed when I had sex the first time.
This is not uncommon, as many women can break their hymen through experimentation (vibrators/dildos), water play (masturbation), tampons (menstruation), or even some vigorous sports can make a girl bend in the wrong way and cause a tear.
You have to trust the girl you're with, and if you're going to sleep with her hopefully you know her enough to trust her, and she knows you enough to tell you the truth.