Does anyone have Crohn's disease, know anyone who has it, or know about it? Diagnosis, treatment, steroids?

I have serious digestive issues and the doctors can't find the root of the problem. Crohn's disease showed up positive in my blood but when they did a colonoscopy they couldn't physically find it in my intestines. Does anyone here have it or know anyone who does, and how they were diagnosed? Symptoms? Treatment? I know a lot of people go on steroids as treatment, and I had a question about that...I heard they make you gain weight. Is it the actual steroid itself that makes you gain weight or is it the increased appetite?