I think you need to break it down and start focusing on the positive. Acknowledge the good choices that you make, the small victories. Like choosing fruit over a candy bar. Feeling good, even when it's a simple thing you accomplished, will propel you into making even more good choices.
Break down your weight loss goals. Instead of 30 pounds, start with 5. It's less daunting.
You obviously love your daughter and part of caring for her is taking care of yourself.