This isn't easy, boomer, Prednisone is a tough medication, and so is Pentasa. I've got my diagnose in june this year, and I have just tapered Prednisone. I didn't get Pentasa.
Prednisone is a medicine that makes your immunesystem work different than before. This makes the small intestine and the colon better, and it takes away a lot of pain. It is ment to take the inflammation away, and it works better the longer time you stay on it. Also it works better if you take Pentasa at the same time.
Try to drink 10 cups of water each day, this could make the headache dissapear. Nice that we are able to poop when we use prednisone, and I hope that it will continue that way after you have tapered Pred. If I guess, I think you will continue to use Pentasa after you are off pred. It's not unusual. (We should always drink a lot of water each day, it helps preventing a lot of trouble in the body)
with all the best from Ingrid