Ulcer or prego??

I am almost 16 years old and my boyfriend and I are sexually active but always use protection. I haven't felt good the last couple of days and have been freaking out about being pregnant. This morning, however, I decided to look up stomach ulcer symptoms. I had a stomach ulcer last year and was wondering if the symptoms I initially thought were pregnancy are actually an ulcer. I've been experiencing pain in my Mid abdominal area, and eating and drinking hasn't really helped much. I'm due to get my next period in a week so other symptoms could be based on PMS. Do you think this is an ulcer or should I be worried about being pregnant still??