Help me please

I am 22/F and this past Christmas my family decided to have smash burgers, tator tots, onion rings, etc. for food.

Basically on the way home I sharted and ever since then my stomach hasn't been the same. I have always had occasional stomach issues and had heartburn frequently. I never really thought anything of it and wrote it off as I probably had IBS and/or GERD. But now I know something is wrong and I am not sure how to move forward

I was having diarrhea after eating anything but felt there was a correlation between fatty foods/dairy? I was also having this constant mild pain in my upper left abdomen. I did the BRAT diet for a bit, went to the doctor, had an xray and blood tests. Nothing abnormal from either of those except a low MCT count which I would 1 off from being in the range. (Lipase and amalyse were normal)

I just kept hoping that it would go away and for a few weeks now I have not been having diarrhea and been eating semi normally but still low fat and avoiding dairy.

Last night I decided to test my limits and eat a bunch of crap for the super bowl and I was fine the entire evening but then woke up at 3AM with explosive diarrhea and felt like I was going to vomit.

I am not sure if this is the right place to post about this but I don't know what to do. I know I need to go back to the doctor but I really want to advocate for myself and my health. I know my body and I know something is wrong but i'm young and I know doctors can be dismissive. I don't know what to have tested? Stool test, blood test, CT scan?? I don’t think I have pancreatitis but maybe something else that has to do with it? idk..