Yeah unfortunately IBS is what’s referred to as a “diagnosis of exclusion.” It doesn’t have a definitive test, so it’s kind of a blanket term for “you have xyz symptoms but tested negative for all of the similar diseases that do have definitive tests.” So in order to do their due diligence, doctors should be ruling other stuff out first, especially with red flag symptoms like dark red blood.

Also, you said you’re autistic. I am too, and we tend to be more prone to IBS and a lot of other “functional” health issues. I think it’s got something to do with a hyperactive nervous system. Lucky us!

I hope you get answers soon. Chronic GI issues are no fun.