Hmmm - if you can't take steroids or mezalazine (mesalamine) I'm not sure what your options are unless you want to try other meds - azathioprine, biologics etc
My alternative suggestion is this, but it depends on where you live and what your personal views are. I've been able to get into remission rapidly with this on two occasions, once when I was about
to have my bowel removed and had nothing to lose (well except my bowel!), but I'll say no more than that as I live in the UK where it isn't legal. If you search on the site you'll see other threads on the same topic.
https://www.healingwell.com/community/default.aspx?f=38&m=3951789