What Causes Difficulty In Reaching Orgasm During Intercourse?

I am a 44 yr old male.. for the last 20 years my orgasm has been decreasing in pleasure??? I Ejaculate but it doesn't feel like anything? I used to sweat, burn up, be out of breathe and it WAS the "GREATEST FEELING " in the world.. Now? I don't bother to have sex or even masturbate because theres NOTHING in it for me?? My orgasm doesn't feel like anything? I Don't break a sweat anymore, my heart doesn't speed up, and it's no longer pleasurable.. is there a cure for this?
I would hate to go through the rest of my life NEVER Enjoying sex again..