pregnancy and postpartum depression

My baby is 4 months old, and I think I’m going crazy. All my life I’ve waited for these moments when I’d be holding her in my hands. And now that my dearest dream has come true, I can’t feel joy. I’m angry and sad. I don’t think it’s how it should be? I worry all the time that I’m doing something wrong. It’s my first child, and I have no one to help. My partner is home only on weekends. My days are all the same, and nights are the worst, I can’t sleep for nights in a row until I’m so exhausted I drop dead and am woken up by my daughter’s screams. I’m mad at my partner, and I feel so bad about it... He almost stopped talking to me. I know I’m being mean and unfair, he’s working hard to support us all. But I can’t control it. A few words he says may make me cry. I’ve never cried so much in my life! It’s as if I’m always on edge, ready to burst. I push myself to get through the day, but it’s getting harder. Why? Shouldn’t it get better? I’m praying that next month it’ll be a bit easier, my partner’s parents will arrive for the holidays to help. But at the same time, I’m scared as hell that my future mother-in-law will judge me. My house’s a mess, I have no time to keep everything in order. I’ve gained weight. I hope my partner won’t show his irritation when his parents are here. I’ve googled about postpartum depression, and I think all the signs are there. But I can’t have meds prescribed, I’m still breastfeeding. Am I even allowed to feel that way?