Orgasm problems (18)

Soooo I can never get past the like 5 second sensation of an orgasm when you’re starting to get it, either when I try to masturbate or getting a handjob from my long time boyfriend, it’s always been a struggle to even get turned on or sexually aroused for me, when it happens I lose feeling in my legs and I feel my vag stremin but then I lose that feeling quickly and it doesn’t happen again later. Any advice? I feel completely desperate