You'll find that many, if not most of the people here have a similar background to yours - not realising the extent of the problem, yoyo-dieting, poor self-image, and so on. To lose a lot of weight often seems like an insurmountable problem and makes the seemingly "easier" course of action (to just give up) more palatable.
But you wouldn't have joined the forum if you hadn't decided to try again and try something different, so the mere fact you're here chatting now and sharing your story is an encouraging sign. Losing weight is simply a matter of commitment and education and attitude. Different people may approach the task in different ways, but at its core is a willingness to change and take control of one's life. It's one of the greatest opportunities a person can have.
So, read the forum messages, read through the main website's excellent articles, discuss, learn and maintain focus. You'll do well.