Upset stomach for 3 days?

It's uncomfortable. Just a warning that this will be a little gross/TMI- no nausea or vomiting, no diarrhea, no loss of appetite. Friday night I noticed I had pretty bad gas that stung and I couldn't poop even though I felt like I had to. I ate a banana and pasta and went to bed hoping it'd be gone by Saturday morning. It wasn't, and I just have this really sour feeling in my stomach. I pooped a few times but small amounts, a little loose. I just feel like I really need to get something out but I can't. I've had constipation many times before but this doesn't really feel like it? It keeps feeling like I'll get diarrhea but I never do. I ate less yesterday hoping it would help and I got heartburn later last night and my stomach still felt nasty. Took a pepto bismol and didn't really feel relief. Woke up this morning and it still feels gross, it's like my mid-lower stomach and it just feels sour. It feels like I need to push but when I do nothing's there. I would equate it to the stomachache I get right before starting my period (not sure if anyone else gets that) but I won't be getting my period for another 2 weeks. I don't think I have a fever or anything and otherwise aside from my stomach I feel perfectly normal and have no other symptoms. What could this be?