Atta girl... You know you're on your way! Forget EVERYONE who ever said you were fat, or ever said you couldn't reach your goals.
I know exactly how you feel and exactly what you mean. I could look at myself in the mirror and want to scream, but then I will see someone who I know weighs more than me and I don't think they look bad at all. We are all our own harshest critics.
Lately I have been trying to overcome this and have a pretty effective (little silly, but effective) way of removing the negative thoughts that I have about myself from my head.
Here's how I do it, when I am thinking something bad about myself I will:
1. Visualize a big chalkboard in my head (green, black, you choose

)
2. Visualize my negative thought on the chalkboard (whether it be words or whatever that negative thought is)
3. Take my giant eraser and mentally erase the negative thought from the chalkboard
4. Write a positive thought about myself on the chalkboard
I know it's a little silly, but really it just helps to clear my mind and help me focus on targeting those negative thoughts and stopping them in their tracks.
I think about it this way... someone says something mean to you, that you know isn't true, you simply tell them to F-off, knowing that they don't have any idea what they're talking about.
Tell that negative-thought monster in your head to F-off, too. Who says it knows what it's talking about!
Know what I mean, jellybean?