how to make him cum?

My boyfriend and I have had sex several times before, but he's only cum 4 times, and each of those times he's had to finish himself off. We'll have sex for hours at a time and he won't be able to cum with out working on himself.
Ive tried giving him the suck, working my hands, riding him, telling him not to play with himself for a week before, letting him do what ever he wants, playing with his balls, massaging his taint, etc. But every single time he cums, he has to spend 10-15 minutes jerking himself. 
It makes me feel inadequate, even though he tells me I'm doing really good. I feel like I can't give him enough pleasure and that I'm not good enough.
Can I get some help from my ladies on here pls 😍