bluefrog,
Welcome to the forum.
If you had flu-like symptoms from the prior use of mesalamines - which means intolerance to them (and it's not a big surprise that the doc won't see it as such), you say you are now on mesalamines again - my question to you is: how are you tolerating them now?
Also, I'm not sure you are aware that deficient vitamin d3 levels are highly correlated to both: IBD and depression.
When were your levels checked last?
And what were they at?
Have you tried any diet modification?
Are you on any probiotics?
If you are interested in adding some simple things which can give you big bang for your buck IMO of course, 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 naltrexone.
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 you.