Just a quick update: I have now stopped my Azathioprine (Azathioprine = Imuran = Imurek) treatment after about half a year with no progress/success.
I was on 50 mg Azathioprine (for the start), then 75 and 100 mg of the medication.
Recently we increased to 150 mg per day which resulted in too many immediate side effects (feeling quite sick, lots of headaches etc.), so I went back to 100 mg and have now stopped altogether.
Nothing planned for the next few months, will try to get my immune system / body "back on track" first before doing anything else.