Is this Irritable Bowel Syndrome or something more serious?

I’ve had constipation and diarrhea. Alternation of both. I dont bloat but i have most of the symptoms for Irritable Bowel Syndrome. I have stomach aches but no abnormal pain or atleast i dont think. The Stomach aches are continuous like. there here for about 2 hours and than there gone for like 5-6 and than there back again. I dont have blood or black stool or mucas in my stool. I dont vomit or have any symptoms of related symptom cancer. I used Whatsmydiagnosis and listed all my symptoms and it said 90.5% sure it was IBS but im not sure if it is accurate or not. i dont have difficulty swallowing but sometimes when i eat fatty food to be specific i feel like it is stuck in my esophagus area. Like my chest area. I try to drink water but it doesnt help. I feel the water going down to my stomach and i can feel the chill water land. I dont eat much so is that the reason i feel the water going down my body and coolness when the water hits my stomach? When i eat something non fatty. It almost never happens unless im like really hungry and im like HECK YA! Food! If that is heartburn than i have it but if its not than no. I dont have a burning feeling anywhere in my body. is this IBS? or something more serious? My bowel movements change constantly because i went a little and than i felt a bit relieved and than about 1 hour and 45 minutes later, i felt my stomach hurt and i went a few pieces of stool again and yeah. Right now im constipated but yesterday i was diarrhea. Is this IBS or something serious? Help! im 13 and i weigh 107.