Could this be an ulcer?!

Could this be an ulcer?

I've been sick for the past couple of days and at first I thought it was the flu. It all started on Sunday night with diaherra and my stomach doing flip flops and churning. So I took pepto bismol. This morning when I woke up and went #2 my stools were a dark colored sort of looked black (my husband says that pepto bismol can cause that. The first time this morning the stool was intact then the second time the stool was runny like diaherra. So I went to the doctor and he told me that it could be something associated with an ulcer so they did some blood work to and I won't know the results for a few days. A few months back I had an anal fissure and the doctor told me to stay away from cheese. I've had issues with ulcers in the past and I was diagnosed with gasteritis in 6th grade and I was told to stay away from certain foods such as spicy foods, tomatoes, anything acidy etc. I had salsa the other day so could that be the cause of my problem and what can be done to calm my ulcer down?

Prevacid.