Help!!!! I’m in pain!!!!!

So this has never happened to me. Today I was in my room just watching tv and then kinda master bating in a certain position on my stomach with something under me, and a get a sharp pain in my lower abdomen where I usually get period cramps...

I am not pregnant (not even sexually active rn), not on or near my period and really concerned what this is.

The pain had died down a bit and I’ve looked things up but I need others help to possibly find out what’s wrong!!!