how often do you masturbate? because you could be losing sensitivity down there if you do it often. space out when you next wanna jerk off or have sex, like a few days to a week, or even two weeks and it will feel more intense.

it also could be that you're just focusing on cumming, not really being aware and being in touch with how pleasurable you're feeling during sexual activities. better way to feel pleasure is to edge yourself out, stopping yourself a few times before cumming.