It is on the WADA prohibited list as being prohibited "in competition", that doesn't mean you couldn't get a Theraputic Use Exemption (TUE) for it. TUE's for corticosteriods used to treat IBD are definitely a thing.
In general terms there's 4 criteria which must all be met for a TUE:
The athlete would experience significant health problems without ...
Talk to your governing body, not the Internet. They will be able to give you accurate advice as to exactly what is and isn't a prohibited substance and the possibility of you obtaining a therapeutic use exemption (TUE).