I agree with everything everyones said above but i also urge you to think serriously about your relationship with your husband.As any relationship difficulties will add to your depression.Your not happy if you were you wouldnt have affairs,Affairs are wrong but that doesnt give anyone the right to be violent.I want to tell you to leave him but its your choice.And i know itd be hard.
From my own personal experience i would urge you to seek help,be completely honest and leave him.But dont think im telling you what to do cause im not im just letting you know my opinion.
Please seek help from a proffesional and do what is healthy for you and your children