First suggestion... relax. Stressing out is not helping your health at all!
I understand - as a Mom we do everything for our kids. I find myself doing nothing for me. Tonight I got my hair cut for the first time in 2007! - how bad is that?! It's like we are martyrs - thinking we don't deserve to be happy b/c of our weight. We can sometimes be in state of depression because we think we can't do this - or worse - don't deserve this.
All I can suggest is baby steps. Tomorrow I want you to do two things.. first - something for your health. (ie. take a 10 min walk, drink 8 glasses of water or eat 5 fruits and/or veggies) and second, do something extra just for you - ie. paint your nails, lock yourself in the bathroom to read (just put a video in for the kids - they will survive)
The key here is not tell yourself what you can't do ... but what you can do.
don't say.. you can't eat chocolate...
say.. I can make a yummy stir fry with fresh veggies.
All the best to you. Post here often.. we are here for you. We are woman and many of us wives and moms. We are in the same boat as you. We should lean on each other.