Postpartum??

I don’t know how to say this... or if I even wanna post this on here but I need help. I don’t know if it’s postpartum depression or what. Ever since I got pregnant with my second child I’ve been so upset... she was a surprise that I didn’t want... it’s been a year since I had her and my feelings towards her are just not as strong as they should be. It kills me to say this and I know I’ll get hate for this but I feel like I just can’t love her. I mean i really care about her, i would definitely care if something happened to her but idk. I’m 20 years old and I have 2 kids from the same guy but he never helps and I just feel like I’m in over my head. I’m crying as I write this because I know no mother should ever think like this but it’s the truth and I just need help. Tell me it gets better... I feel like I’m so alone and no one understands me or how I feel... please help