I don't want to be a dad.

I'm 25 and my girlfriend is 24. She is currently 33 weeks pregnant. We found out that she was pregnant back in July 2022 and since then my life has been upside down. I have absolutely no desire to be a dad and I feel like I'm just going through the motions. I feel like I'm trapped in a never ending nightmare. I just want my old life back and I feel like this new life that's being forced on me is just ruining my life. We were on such good terms and we had a great relationship up until July 2022. We now constantly fight and have absolutely nothing in common. I feel like it's only getting worse and I'm just burning out. I've tried to talk to my girlfriend but she just gets angry and tells me I'm immature. I'm just so lost and I don't even know what to do. I just want to say that this is not what I wanted.