Well, can he cum from jerking off? If that is the case, then I don't think that it's anything more than performance anxiety. Maybe he doesn't know what to do, or has lingering questions on whether or not you're enjoying it unless you're driving the act. No worries though, it is all very fixable, however it may take some time. Start slowing things down, and maybe get rid of sex for a bit, and switch to mutual masturbation to see if he can still get off. If not, then let him do it and you just nibble on his neck or something of the sort. The idea is to get him cumming around you. And then, when he is comfortable with one step, take it one step further.

Also, if he's not getting off and you're just getting tired, don't just hop off him and feel sorry for yourself. I can tell you that as a man, it really hurts to not be able to satisfy your woman. Hop off, jerk him off or let him finish, then smile and sit there with your naturally womanly glow. Don't allow any negativity into the bedroom. It's just not cool. 

Me and my wife had the same problem for 3 moths then we came to the conclusion that we should do oral sex before then jump to intercourse..It doesnt take as long to ejaculate.nd if that doesnt work you should just give up:)