My boyfriend won't tell me why he won't cum

So me and my boyfriend have been having sex for about the past month now. We've had sex maybe 4/5 times now and he hasn't came. Just to be clear we are 17 and 18 and live with our parents so we can usually only get up to an hour to do stuff. One day I decided to have a talk with him on what I could do to help and he said "trust me it's not your fault blah blah blah you're the best i've ever had etc etc" and i don't think he's lying about the best he's ever had part because he's only had sex 3 times besides me. There's a high possibility that it could be his anti depressants that I'm not supposed to know he takes (his friend gave me a ride home one day and accidentally told me because we were talking about how we care about him and want the best for him). I really care about him and want him to ya know, feel good. Is there anything I could do that could help him talk to me about it or maybe something that I could do that will just blow his mind to help him finish?