your not eating nearly enough, which may sound crazy, but if your only eating 1500 calories a day your metabolism has probably grinded to a screaching hault, you cant continually eat such a huge calorie defecit without your body adapting and slowing your metabolism. Are you taking any supplements? fat burners etc? post your diet for people here to tweak for you too. Also, in my expierience it is very hard for people losing over 100lbs to get a tight look in the lower abs and back because of loose skin, start moisturizing that skin like crazy with some kind of colagen cream. That skin will tighten up in time, but how much will depend on alot of factors.