condoms

Me and my bf have only had sex on other time but we ended up not using a condom because it was his first time and it was too small.  I have always used condoms and I would like to use them with him but when ever I bring it up he says it's hard to use them once you haven't used them. But how does he know I was his first time. What should I do in not sure I feel comfortable not using them I'm only 19 and I still plan on going through med school I can't get pregnant!