Doctor thinks I have an ulcer or ibs is he right?

Hello everyone. it’s my first time here so I’m going to just jump into the explanation. Saturday I woke up with this terrible Lower left stomach and back pain to the point that I couldn’t look down or my back would ache. I did no activity but I am a heavy guy so I ignored it for a day. The pain still didn’t leave so I called my doctor that night. He told me to go to the er as soon as possible and get a ct scan to rule out appendicitis. I went and they did a ct, blood test and a urine test. Surprisingly all of the results are normal. Er doctor says that I should increase fluid and move more. I listen. Pain is no longer in back but it is still in my whole stomach and it’s also primarily in my right side. It’s not excruciating. I can still move around just pain but it’s there. I video chatted my doctor again and he asks me a series of questions. He comes to the conclusion that it could be an ulcer or ibs and gives me medication for both. One will be at my home later today while the other doesn’t get delivered till tomorrow. I understand that I am big but I don’t drink or smoke anything. I’ve asked is it appendicitis only to get told no because I’m able to be active. Is this normal or possible?