Tmi idk whats going on

Ok so i use to be a really active and healthy person, my bmi was 31 but on a 5'10 large body frame.... well short story i got addicted to drugs and then got sober... in the last year i gained 100 pounds and my blood pressure went up.... now that ive been sober for awhile i decided to start working out and eating healthy... well heres the tmi... everytime after i have a vigorous workout i get a stomach ache and diarrhea.... this last time i barely made it to my bathroom at home.... anyone maybe know what might be the issue???