I'm too poor to afford a vasectomy and freezing sperm, and I want the experience of cumming deep inside my girlfriends tight pussy (took her virginity). She's on birth control and I know she takes it correctly and perfectly (I ask her every few days, she shows me and she also doesn't want kids either). I've read that cumming in her pussy when shes on the properly taken pill has an extremely low chance of impregnation. How true is that?

I don't want to make it a regular thing either, I just want the experience of dumping a load into her pussy once, and then i'll go back to using condoms or pulling out.