Black Stools and Stomach pain?

Hello Everybody! For the past 2 months since I started my new job I have had chronic bowel problems. I have disregarded it as me being overstressed however I think now it may be something more serious. The day before yesterday I started having terrible stomach pains in my upper stomach that also radiated to my back. It felt sort of like a muscle cramp in my stomach and it was constant the entire day. It just got worse and worse to the point where I couldn't stand up straight. When i got home from work I noticed that my stools were black and even going to the bathroom didn't releave the pain. Finally I decided to go to the ER. At the Er they tested my stool and said that there was some blood in it. They also tested my blood and said that I had a high white blood cell count. They said they thought it was ulcers but they didn't do any further testing. They just said that according to my blood it doesn't seem to be life threatening and that i should schedule and appt with a gastroenterologist. They gave me some medicine to help with the pain and since then it has been more tolerable even though it still hurts especially during and after eating. My question to yall is, If you've had similar symptoms what was it for you? What kind of testing should I expect? Thank you for your time!