Depression and children?

I have four boys - 10, 12, 15 and 16. After so many years of nothing but fighting and arguing it has gotten to a point that I just find happiness in absolutely nothing. No hobbies, no time to myself (single mom), I mean, I truly find getting up every morning as a chore. My boys rarely get along and have no qualms about making a scene in public.One of my middle children have ADHD, Tourettes and BiPolar combined. Any recommendations?