You mentioned 'doormat'. That is important. If that was how you felt, believe me that he wasn't the 'one'. I had to walk out of a marriage where I was fighting not to be trodden underfoot.
You will be OK eventually, honestly. Longer-term you may even be glad. (I think you will be.)
Sqad is right in that anti-depressants will help you over the start of this. They will enable you to rejoin normal life. Join a choir or something (singing releases serotonin, I believe, anyway, you feel better), see more of your friends and family, treat yourself to some new clothes now you have lost weight. Eat little and often and things you like - even if it is chocolates for a week!
I do know how this feels. It won't be quick, but you will heal. :) x