Sex question

So I have been dating this friend of mine for a couple of months now and I finally decided I want to sleep with him. We really like each other and love spending time together. However, every time we are about to have sex, he puts on the condom and looses his erection. He told me he is not used to condoms and never uses them and I don’t want to have sex without protection plus I don’t take birth control. I don’t know what to do because I am not sure I want to start taking birth control and I don’t want to have unprotected sex but I really want to sleep with him! Any ideas as to why this might be happening?? Any advise??