You're not greedy though. That's an outdated opinion science no longer supports. Being fat doesn't mean you're greedy and lazy. It means you got a poor genetic hand in a world where obese-inducing food is virtually impossible to avoid.
The chances are if you're fat then you've got exactly the same amount of willpower as a thin person, but they don't have the level of food noise, hunger and biological drive to eat, eat, eat.
You might need to be on the medication forever, because obesity is a disease we can treat but not cure. People with high blood pressure can sometimes enact sufficient lifestyle changes to come off their medication, but it's rare, so they take medication to combat it. Obesity is no different, medically.
Society, however, is taking a while to catch up. And it's going to take us a while to let go of the 'I'm like this because I'm greedy' mindset that's been drilled into us since childhood, that it's a moral failing, that we're somehow lesser than thin people. We're not. Sorry, I've gone on a bit there. But - you're not greedy.