6-mp is an immunosuppressant often used if 5-asa is not enough or if there is prednisone dependency. It would be best if you googled it because there is a lot of information about
how it works, what its side effects are, ... etc. No posting here is going to give you as much info as you get reading the 6-MP wikipedia page.
I think you are bleeding because you have solid stools. The far end of the colon/rectum is inflamed and subject to bleeding. The hydrocortisone shoud mitigate bleeding some, and the 5-asa suppository should start to reduce the inflammation (but, as noted it may not be reaching high enough.). I suspect if you had poorly formed stool there would be less bleeding. Moving a well formed stool through an inflamed and ulcerated section of the colon is going to result in some blood.
I think the key issue is whether you are slowly responding versus not responding because the meds are not reaching the right spot, or the underlying condition (i.e., affected area) is getting worse. You can wait out the former, but the latter needs a change in regime.