PREnatal depression?

Hi mamas. I'm a FTM, 20 weeks pregnant and after being unusually down for the past couple months, I contacted my Dr who told me I had Prenatal depression (depression whilst pregnant). My pregnancy was unplanned and a complete shock and it's taking me a while to adjust to the idea of having a baby. There's also been huge trouble with my mum and also my In laws, so my life isn't exactly stress free. Don't get me wrong, I love my baby already, but I can't help feeling sad most of the time. I cry almost every night. I'm just not my normal self at all. I feel like a freak. Most women are happy during pregnancy, so why aren't I? I feel like such a bad mum already :( I was just wondering if there's anyone else who has experienced this? If so is there anything I can do to make it better. I feel so alone :(