How do i get an ephiphany in losing weight?

I'm a pretty chubby, ok obese. I'm a young 20's something women. I want to not only look better, but I want to also feel better and healthier. I'm getting to the point where I will want a baby not to far off in the future ( the point is minute). I don't have any health problems, no diabetes, not hypertension, nothing. I don't know if this is what is holding me back or not? I always put myself on a diet, and exercise regulary (2 hrs a night). Then I always quit, and then i'm off for a month or so, then go back to the whole diet regime. I can never stick with it and I can't muster up the will power or motivation to just keep going. & before i know it I will have all those health problems and not be able to be healthy for the future things. but all in all, where do I find this motivation to keep going? I really don't know how? Any ideas? Help? <3