You didn't define not working. Regardless, iron will not help the agony or loo visits due to diarrhea. In fact it may be the source of your problems. Iron tablets, can and usually do irritate your stomach causing gastritis. That's a upper central to upper right quadrant pain. It usually makes people 'loose' as well. So that might be causing your loo visits. Are your blood iron levels so low that you can't stop taking the iron, probably not or you would be getting iron injections or transfusions... Even if you stop the iron tablets gastritis can continue because your stomach acid is now attacking the inflamed lining. You might need the likes of omeprazole to stop the acid production for a while allowing everything to settle, if that's the case. You should see your GP tomorrow about whether you can stop the iron or change it to a different formulation; Sytron a liquid iron is easier on my stomach, and whether your pain includes gastritis.
So back to the agony. Where, what, when? you need to think about this to get the best out of anyone here, or your GP, or the registrar/consultant you see at the hospital. Just saying its not working, wont help anyone to help you.
If it isn't gastritis, from the iron, it might be pancreatitis from the azathioprine. Or some other azathioprine related thing. Combination of entercort and azathioprine should see you improving, but it might not be strong enough to be complete in itself. So another pack of pills may well follow, and they might not work either - welcome to Crohn's, it stinks.
How long have you been on the azathioprine and how much? days, weeks, months, are you still getting weekly blood tests? If you have only been on aza a few weeks it may well be pancreatitis as these things generally appear in the early stages. So does the pain radiate to your back?
You said pred didn't work earlier. That's most unusual. Pred should do something. Have your doctors mentioned surgery. Have they done any tests to determine what's going on?... like colonoscopy, gastroscopy, or small bowel follow through?