need to keep my weight down after surgery

I am getting surgery n xt week and I need help losing the weighg and kkeeping it off. My thyroid is getting removed ad now my metabolism will be at normal levels while now it is high andim still gaining weigt while its high!!!! Just need a push. I always give up. And I have a 15 month old and never have tie to work out (sorry about the misspellings. My phone keyboard has a mind of its own!!!!)