Welcome to Healing Well! You're definitely in the right place.
Here are two links that provide some information regarding "indeteriminate colitis". Hopefully they'll provide you with some insight. It sounds as if the term is a catch-all for inflammation of the bowel that doesn't yet have a cause or diagnosis.
The esophagitis and gastritis definitely put you in the same league as many who post on this forum. It's a very uncomfortable condition, and I've experienced it multiple times in my life. I found it difficult to eat when I was in the throes of a bout of gastrits and esophagitis. Be sure to eat very carefully. Only smooth foods (that have been chewed to a creamy consistency before swallowing), no spices or acidic foods, and no alcohol. It's a long-term project to heal GI tissue that has been inflamed.
I don't know if you doctor would agree, but I have always found that Carafate Suspension is extremely helpful in aiding healing. You might ask about it. It's only available by prescrption, and is quite expensive. If you have good prescription coverage it won't be a problem, though.
I would guess that they may be linked just in the fact that your GI tissue seems to be reactive from one end to the other. Reactive tissue takes time to calm down. Healing them will take some time. It was always at least 2 months before my upper GI tract was feeling better.
Yes, unfortunately, it's very common for doctors to take a long time to follow up on testing results. The good news is that if there was something very serious you'd be called right away, so if they're waiting, they must think it's not a big problem.
Good luck getting things feeling better!
Again, glad you've joined the forum!
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”