Cramps after Orgasm?

So for the past 2 years or so I’ve been getting more into discovering my own body and recently (last year or so) whenever i masturbate (clit only for pain) i have intense orgasms where my whole body locks up and shakes but afterwards i get these unbearable cramps and back pain almost like period cramps x10 that last ages. I just wanted to know if anyone had the same thing happen to them or knew maybe what could be going on? Thanks xxx