Pain in lower stomach, 2 problems.

FIRST PROBLEM: I woke up this morning with a terrible pain in my lower left side of my stomach, I have had this before but never got it checked out since the pain was tolerable but today the pain has gotten worse from the last time I had this happen. It hurts when I walk, cough, lie down and even when I am sitting down. I read a few posts about similar symptoms but didnt find an answer.

SECOND PROBLEM: My other problem is that when I eat something sometimes (this happens at least twice a week) about 30 minutes later I get a terrible stomach ache to where its almost unbearable and then finally I get diarrhea and I feel better but most of the time it takes up to 3 hrs or more for my stomach to completely settle down. The last time this happened I was running in and out of the bathroom for almost 4 hrs with diarrhea and the most severe pain I have ever felt from my stomach. Sometimes the first time that I have to go to the bathroom from the pain its just regular stool and the last time I looked at it some of it had a bit of black in it. If you know what the problem is PLEASE let me know so I can go to the doctor's. Thanks!

* I have never used this site to ask about a problem so I dont know if this is in the right category or not but if not, I am terrible sorry.