Altering diahrea and constipation. Them?

6 months ago i went to the ER because i was using the restroom more than 6 times per day for a couple of days. I was low on fluids had the chills and bad cramps. Had a catscan and was told i had colitis and to follow up with a gastrologist. I didn't because i didn't have insurance. 6 months go by and throughout that time I've been fine besides waking up sometimes feeling like i just ate at a buffet (very full). Recently ive been getting the same symptoms as 6 months ago so i went to my moms doctor who said he doesn't think i have colitis but maybe irritable bowel syndrome. He prescribed me a medication to help with diarrhea. That wasnt very satisfying for me because now i havent had a bowel movent in two days and i have horrible cramps. I looked into probiotics and they say that works. But there are different kinds amd different strengths and to get a doctors advice first. What do you think about the probiotics? At what consistency should i take them? Thank you so much.