Hungry all the time. It's mental, I think?? OPINIONS PLEASE!!

I had my surgery in Aug of 2008. I have gone from 324 pre surg weight to 165. I am hungery all the time. I snack all day long. Mostly healthy stuff fruit, nuts and I'm lucky enough to still be able to eat popcorn. The fact is thats all I think about. I cannot eat much at once but I can go all day. grazing like a cow. Im scared of gaining but I am not even sure about that. Im happy to be where I am but the doctor says I should be at 145/150. Im happy where I am. I dont even know whats going on in my head anymore. Confused?? Please other perspectives PLEASE!!