Causes for abdominal pain

I'm a 17 year old male. About 5 months ago i started having really bad abdominal pains, I went to the walk in clinic and he told me i had gastroenteritis, And told me it would pass in two weeks.. Never did pass.. and over these 5 months i have all kinds of test done to me blood work, colonoscopy, Cat Scans, X-ray's, Stool Samples... I have been given pills for ulcers... Inflammatory pills ect.. My abdominal pain has gotten better over time.. Now it just hurts until I defecate, or i am really gassy and have to fart to have relief. I have seen about 4 different doctors and none can find the problem. Ive been to a gastroenterologist after allot of my test were done. And he told me all the tests he has done came back negative.. And i mention something about Anxiety and he totally switched subjects and thinks that is the main cause.. I never had any anxiety at all until long after these problems started.. I really do think there is something wrong and can't find what it is..or what angel to approach it at next.


And also my pain has been better after trying a none gluten and dairy diet.

I have also had other symptoms such as having to urinate allot more, Being light headed every time i get up, sweating in my sleep, Feeling weird, can't really explain the feeling just not normal.

Any idea's or information would be really appreciated.. i really is hard for me to stay at home for 5 months and only have this on my mind.

Thanks
-Colby