Tense, short of breath after ejaculation

Every time I masturbate I tense my pelvis subconsciously and what started out as wanting to prevent ejaculation and just feel prolonged pleasure.

Now I think it's gotten so tense that when I actually ejaculate I barely reach orgasm and it's really frustrating. It's been years since being able to feel real pleasure and the peak of orgasm without tensing so much I lose sensation and feel like I'm forcing it out.

Does anyone know how I can relax the pelvic area or enhance pleasure, it feels so numb and uncomfortable.