Side chick pregnant

So back in September I went out with this guy from high school. I was surprised he asked me out as we hardly spoke back then. We went out a couple times and then he just ghosted me and I never knew why. I didn’t mind really as I’m not the kind to get attached easily. It was just annoying as he would watch my stories allll the time still. I was on FaceTime with my best friend who goes to school with him, and she just happened to be hanging out with another girl from high school. I said hi and after she left my friend told me over the phone that her and the guy I went out with a few times were together . I asked how long that was going on for and she said ONE YEAR. I hadn’t told her about how I went on a few dates with him as it wasn’t serious just hooking up and I didn’t know what to say.

His social media has nothing of her and he never mentioned her obviously. I messaged him saying “you didn’t think It was important to tell me you were taken?” He just responded saying lol and asked me not to message him again.

Fast forward a few weeks and I find out I’m pregnant . I posted the ultrasound on my story as I knew he’d see and he messages me right away asking if it was a joke. I said no I’m really pregnant and he said congrats. Immediately after that he completely blocked me on all the social media I had him on . I haven’t told anyone who the father is and I’m not sure what to do. I don’t want to message his girlfriend and cause problems as I don’t really know her, and honestly I feel like if he doesn’t want to be a part of it then fine I can raise the kid on my own. Is that wrong ?