I was around 4 an a half/5 stone off years ago, just done calorie counting an upped my exercise, it took forever, like none of it was fast an there was times I was getting truely dissapointed because I'd go a few weeks losing 1lb or 2lbs then weeks where I stayed the same or maybe gained a lb or two again, but I've never regained anywhere near what I lost, I do go back an forth now, a lb gain then a lb lose but I've kept around the same weight ever since then when I originally lost it all, I am gaining a little bit now but I know it's cause am not being as active as I should be
You have to be strict with yourself an it does take a lot of will power, I wouldn't say you should deprive yourself of the "junk" food as you end up on a binge, but use it as more of a reward like you have so many good days then a little reward then back on track etc
But don't give up, it can be done an they always say the slower it comes off the longer it stays off, surgery isn't always the answer either, you have to have some amount of control with that as well, I know two that got surgery that are now bigger than what they were before they got it because they assumed the surgery would fix it an could still eat whatever, you are still technically doing a diet with surgery, it's just giving you a helping boost