I used to weigh 260.5, then in a year went down to 168.5. I couldn't shift any more and have since gone back up a bit, but am now on my way back down again. There are lots of us here who are in the same boat, or who have been, and we all know what it's like. There are some real success stories here, who have lost all their weight and kept it off, and you can look to these people as a real source of inspiration! If they can do it, there's hope for the rest of us too. Try to look at it in small tasks, eg try to go for 10lbs at a time, something like that. It seems a lot easier that way.
The only advice I can really give is to don't keep putting it off. I'm 25 now and feel like I wasted a lot of years because I wasn't doing anything about my weight and it affected my self confidence totally. It stopped me from doing a lot of things I would have done if I'd not been so overweight. You can do it, but it takes time and patience and a **** of a lot of strength. People here will help you with that.