Why is foreplay such an essential for me to cum during sex?

My boyfriend and i have sex 5-6 times a week. Usually its amazing. But, it seems like im doing most of the foreplay. He begs me to go down on him or to jack him off before sex, but if i ask, then.."theres not enough time" or "i want you now". So he jumps on top of me and screws me anyways.

I want a better build up..but i dont know how to make him see that. Ive tried talking to him about it but apparently that didnt work.

If i cant get him to get me off beforehand, then how else do i make sure that i cum during sex? Im so sick of this sexual frustration thats occuring more and more often..

Please help.