Is it depression?

Sorry for the rant as this is probably gonna be long winded, so since I had my little girl nearly 2 years ago, I feel like my whole personality is changed, I had quite a traumatic birth. I’m not one to open up or talk about feelings so I just deal with everything in my head. I am generally a happy person, I have a home, a partner & a little girl. But I also know depression can come in different forms. All the time I feel this bitterness towards everyone, like I want to be mean and angry towards the ones I love. I don’t ever want to be happy for people, I just get this over whelming urge to be horrible & unpleasant. Before I had my little girl I was nothing like this, I know it’s full on being a mum & that doesn’t help. I am quite lonely as well which doesn’t help, like I said I don’t talk to anyone as I dont have any friends. I’m just so full of resentment all the time, I thought it was a postpartum thing but 22 months later it still hasn’t gone away. Any advice I’d really appreciate & thank you for reading if you’ve got this far. X