Post nasal depression

I’ve suffered with depression and anxiety since being a teenager but have now developed postnatal depression. I’m really confused as to what it is because I don’t resent my baby; I love my baby so much. I just feel I’m not enough and not doing enough. I feel suicidal and have suicidal thoughts a lot of the time, where it takes over my thoughts and that’s all I can think about. Are there any groups with first-time mums experiencing the same? Where can I take my baby? Looking for other mothers who I can relate to, and we can support each other. I’m really struggling. I live in the south Manchester area and don’t drive. I don’t have any friends or people I feel I can confide in and trust without being judged. I just feel so lost and trapped. I don’t know where to turn. I just want to be happy again, and I want my baby to see me happy. The relationship is very up and down with my baby’s father. I moved back to my mother's with the baby, as I didn’t feel supported, and there were lots of arguments. It’s very up and down. I feel he doesn’t understand mental health, although he says he does and wants to help. My mother and sister get impatient with me and frustrated, saying, Isn't the baby enough for you to live for? You shouldn't feel like this because there's nothing to be upset about, and you need to pull yourself together. They do support me in some ways, but then in others it can make me feel a lot worse and angry with myself for feeling this way. It's hard not having friends to speak to who I can trust, or even my partner. I feel really lonely and lost. I feel very disconnected and disinterested in everything. I feel like I’d rather shut down than open up or tell the people around me how I feel because they seem very confused as to why, and it makes me feel worse because they don’t understand. It’s very frustrating. I feel angry a lot sometimes because I can’t even understand why I feel this way; it’s just not making sense to me. I just needed to let this out and see what help is out there. I appreciate any advice.