Your body has reached its new set point. Losing more weight will be as difficult as losing weight preop, and as difficult to maintain that loss.
Others have discovered that (for example), to maintain 130lbs, they had to eat 1100 calories a day. To maintain 150lbs, they could eat 1800-2000 (they were also exercising).
So, you need to decide how important those last 20lbs are to you. You'll have to restrict your calories and exercise more to burn them off, then figure out how to eat/exercise to maintain.