nuvaring+cum inside?

so my boyfriend and I have been having sex for a little while now and I'm on the nuvaring for period stuff and that's what we use as birth control. We also use the withdrawal method, just in case. He talked about cumming inside and felt pretty comfortable about it, but I was like no way, I don't want to risk it. I know this isn't important really but he wants to be a doctor and I want to go to this crazy hard college so we REALLY can't get pregnant right now... He was totally fine with me not wanting to, but I could tell he wanted to try it. I'm worried about the stress of the added risk of him cumming inside, anyone have tips?