Welcome to the forum and hopefully you will get some information that will be of value to you.
Reading over your post reminds me strongly of some of the problems I'm having with one of our cats. It could possibly be very similar in nature for you.
If I were you, I would do some research into food allergies and food intolerances. This has the appearance of being a food intolerance - either a protein problem or a carbohydrate issue.
I would be taking it up with your alternative vet or your allopathic vet - whichever one you feel comfortable with. I would think that a menu change could rectify the problem.
Our cat was having the same sort of issues with the bloody stool plus lots of gas - we could hear her all over the house when she went to the litter box.
She has had a complete food change recently eliminating anything containing poultry protein, and this seemed to be her problem. I'm not saying it is your problem, but it's worth looking into.
I have been in and out of the vet's office over a period of years with this problem and it was just recently with a new vet who suggested the diet change before doing any scope work or any other procedure.
It appears that food intolerances is one issue that is missed by the vets quite often, and they start treating for IBD.
Hope this helps. Keep us posted.
Hazelrunpack's suggestion of a veterinary school teaching hospital is an excellent one to follow up on. Speak to your vet to get some idea of costs.
My vet says that they are relatively expensive when I questioned about an MRI for instance.
Animals are such agreeable Friends.
They ask no Questions. They pass no Criticisms.