Is this IBS? I disagree with the diagnosis.?

I have GI problems every single day and a day never goes by where I don’t feel well. There are times when I get VERY sick and stay home for weeks at a time - but I am never 100% and always feel terrible. It doesn’t come and go..but it does get worser at times.
I usually feel worse after I go to the bathroom. I have had a lot of tests done - colonscopy, endoscopy, small bowel follow through, ultrasound, celiac test and other blood tests. My symptoms include constipation, but when I do go it’s narrow and sorta formed. (I take Metamucil which has helped a bit, but not that much). I am very sensitive to heat because of this and when I eat warm food my whole body feels warm. I also feel this mild nausea, especially in my eyes and I tear. I also have pressure headaches where it feels like blood is rushing to my head. I have also noticed my legs and arms fall asleep somewhat frequently.
The doctors don’t think it’s IBS but said there’s nothing else it can be - they say severe IBS.
I have also gone off wheat and dairy for long periods of time (> 6 months) and had my allergies tested. I tried naturopathy as well.
And I’ve had this for about 5 or 6 years now. And a sigmoidoscopy makes no sense! A simoidoscopy only allows for view of the lower part of the colon and colonoscopy views both top and bottom. Don’t try to make people paranoid on this.