You need to see a Gatro doc to find out what's going on. Having a colonoscopy only to find out you have IBS is wonderful! You've ruled out all other causes, can be treated for what the problem is, and put your mind at ease. A win-win situation. Plus, he may not feel at your age that you need a colonoscopy, he may know from your symptoms what it is. This is their specialty, you've suffered long enough. It's time to stop guessing and get to the bottom of what is wrong, so you can start living your life to the fullest! Take care...
It may just be bacterial. You cannot predict the future and things are hardly ever as bad as they seem to be. What you're going through now is far worse than what you are afraid of. See a GI doctor
Check too see if you are a Celiac. The diet and diag. for me is a lifesaver.
You could try a food elimination diet - remove dairy for 4 to 6 weeks and see what happens.
Could be a parasite - have your stool tested
Could be IBD (irritable bowel disease - different from IBS) - colonoscopy will be the only way to determine this. My 4 year old has had three scopes in the last year - I'm sure you can do it! It will be worth it to find out what is wrong.
Good luck.