just to clarify, when you say colitis, do you mean ulcerative colitis (UC) or just colitis? I ask because ulcerative colitis is a form of inflammatory bowel disease. Colitis simply means inflammation of the intestine, which can be caused by many things such as food poisoning...
Anyway, in answer to your question, migraines are definitely not a common symptom of UC. However, I imagine there are a few factors that could contribute to migraines, such as dehydration, which can be a problem for people with UC. However, dehydration risk usually increases due to things such as diarrhea, so if that's not a constant thing then that's likely not it.
As for having been there all along just not diagnosed, IBD is thought to be linked to genes, so many people are predisposed to having IBD, which is "triggered" at some point by something external. Some people have their first flare during pregnancy for example, or it could be as simple as something in the environment.
Hope that helps!
- Sahara (team member)