Welcome to the forum.
Sounds to me like you are intolerant of the mesalamines based on what you described.
Also, on the side effects listed for the mesalamines it says it can make your UC symptoms worse!
Anyway, your doc doesn't believe stress and diet has anything to do with UC - what an idiot! Those are major factors in UC, IMO.
Besides slippery elm powder, you can also try l-glutamine.
Are you on any probiotics? they are impt
What are you levels of vitamin d3?
They should be in the high 50's IMO, and yours are probably in the lows teens or twenties.
I hope you start to feel better soon, and if any of these things interest you, there are things IMO that you can control, which will have a direct impact on
your disease, the symptoms you experience and their severity.
I was able to control my UC into remission through various
supplements, probiotics, diet modification, and LDN , low dose
For more info on the protocol which has put me into remission,
please go to this link: https://www.healingwell.com/community/default.aspx?f=38&m=1666318 , and look at the 11th post.
I hope you feel better and let us know how we can help