Post partum depression?

I am 29 years old. I had this pregnancy perfectly planned. I had money saved up to be able to stay home with the baby. I had the baby last July. He had colic where he cried nonstop for hours for the first 3 or 4 months. I tried everything and went to different drs, finally it went away at 4 months. He is now 6 months old and doing so much better but he still wakes up ever 2 hours at night some nights. He still has his crying fits ocionally. My husband works all day so I am home by myself most of the day. I want to meet people but sometimes I cant get my out of the house and I havent been making an effort. I feel alone. I feel this pressure. I feel hopeless. I dont know if it will ever get better. I used to be a successful workaholic but now I am a stay at home mother. My life has totally changed. I need a break but I wouldnt dare leave him with a sitter. I just feel this weight on my shoulders and feel hopeless about the future. What should I do?