How do I know if I suffer from post partum depression?

My baby is 5 months old and i have a 5 year old and 3 year old at home with me all day and an 8 year old in school. My husband is a good support to me but it just doesn't seem like enough. I just wanna cry right now because my house is over whelming. Just the smallest task is overwhelming! My children are mostly a bother, when they didn't used to be. I am totally sleep deprived. I am fine in the morning but tend to feel this way more into the afternoon and evening. When i take a break from life I feel better, but then life comes crashing down on me again. I hate my body right now, I know I should work out but feel like what is the point cause I am gonna be interrupted by the kids. Cannot afford a gym membership, and getting up early is out of the question. I sorta feel like I want to scream and let loose on anyone who comes near me. So am I post partum or am I just tired?? I don't want to hurt my baby, or my children. Well.... to be honest I do think it would feel sort of liberating to them really hard, but only when they mis behave, but I resist. What do they give you when you are post partum depressed and how does it help?