birth control and sex

Ceci

So I've been on birth control for about 4 months now because my doctor diagnosed me with PCOS and im moving in with my boyfriend in June. I thought about having sex without a condom because hes talked about it and he seems to have quite a fascination for it. If he cums inside of me what are the odds of getting pregnant? I'm on the Costco generic version and ive been taking it for 4 months straight.