I deal with negative self-talk too, and one thing that helps me is positive affirmations. It feels REALLY weird when you first start, but it gets easier eventually, and after awhile it becomes a habit. Plus, it's easy. Here's what I do:
I wrote the following phrase on a Post-It and taped it to my bathroom mirror:
I accept myself unconditionally RIGHT NOW.
Every morning and every night, I look at myself in the mirror and say it out loud. It sounds stupid, right? But it really does change the way you think about yourself over time. Plus, it's free and easy, so there's nothing to lose by having a little chat with yourself in the mirror a couple times a day.
I wish you luck. A negative self-image is a very difficult thing to overcome, especially when we don't feel like we deserve to overcome it. But it can be done, I promise. Losing weight helps a lot with that as well, as long as you can learn not to beat yourself up about set-backs and slip-ups along the way.

Hope it helps with the weight thing, but already know it's helping with my attitude and overall wellbeing.