My bet (after being on Prednisone 4 seperate times and having lost the weight from all accounts) is that you will start to notice changes soon. Most of the weight is probably water weight which is a common side effect. There are LOADS of support groups for people who are on or have been on the evil stuff. (I have made the decision to never go on the stuff again. The side effects were so awful, esspecially on the really high doses I was on (120 mg/day!!) that I was in total agony the whole time.)
Give it some more time before you think about diet pills. Check out the 'net to see what other Prednisone users have said about weight loss. You are young (25, right?) so you shouldn't have troubles. I was 21, 23, 25 and 28 when I used the stuff (32 now).
Good luck, I hope the spray nasal rinse works for yoU!