Weight loss stopped...?

Ok, so I originally started this at 245 pounds; which I'm happy to say is now 220. My goal is 200, and most days I follow my eating plan and stay under my calories goal. I drink tons of water everyday, and as far as exercise goes...I walk a mile a day on days I don't work (job is 6-9 hours of being on my feet walking around) and pay badminton with my family on days we play. But, for some reason, I can't seem to break below the 220 threshold I'm at. No matter what I do our eat, I stick at 220. I'm not sure if this is just as low as I can go or what...because I still have a decent amount of fat on my upper body. If it makes any sense, I'm also on Prednisone (have been tapering for about a month) and I have rather slow, infrequent bowel movements as a result..sometimes days, and I wonder if that might play a roll.

I'm honestly at a loss...is 220 as far as I can go and just need to tone the fat off my upper body and back? Or am I doing something wrong?