Well, I'm sorry but I'm afraid I cannot agree with that attitude. What can the vet tell you? Well, he/she can examine and do tests which might actually find out the problem, instead of guessing at it. And he/she can give you a medication and dosage which is appropriate and backed by scientific literature.
Yes, stress from anything, including a vet visit, might be a problem - but continuing home remedies in the hope that one of them gets lucky is not the answer.
I really hope he gets better.