What is wrong with me?!?

I'm not sure where to start... I guess with the problem that is frustrating me most which is pain and diarrhea at least once to twice a week. I usually (as in for months now) can only go to the bathroom maybe once a week or so. I will be incredibly constipated for that week and not be able to go no matter what I try... then it never fails after about a week I feel the stomach ache come on and will inevitably spend up to a couple hours on the toilet. First I will just have regular but painful BMs but then it will turn to diarrhea - it does every time. I have a cyst on my left ovary, which is where the descending colon comes down and that pain directly coincides with the BMs every time. I just don't understand if the cyst is CAUSING the tummy trouble? Is it blocking me from being able to poo when its swollen up? And why the diarrhea? I am miserable!