My boyfriend take forever to cum

My boyfriend and I have had sex many many times and not ONCE has he came EVER. The longest we've had sex for is a straight solid 4 hours with 1 hour of foreplay prior to that and he didn't cum at all. I managed to suck some precum out of him but that's about all I got. We plan to have kids and get married but how can we have kids if I can't make him cum? I have tried all sorts of little trick to get him really going before we have sex but it seems like it's not enough. I will talk dirty to him, wear his favorite outfits, wear sexy under garmets, touch all his sensitive places, tease him and more.I know it's not because Im loose because he is the first person ive ever had sex with. I just don't know if this is normal. I mean 4 hours!?