I've had a similar experience OP, my baby is 9 months, he left when I was 28 weeks pregnant - didn't even tell me, my landlady did!
Only differences are that he came back a week before baby was due (not to live, we still live apart) and we've been trying to work things out until he disappeared for a month after I contacted CMS as he wasn't pulling his financial weight. He's now back in baby's life receiving therapy.
What you're feeling sounds quite normal, I blamed myself a lot for a lot that's happened over the past year but thankfully I have a counsellor through my college (I'm 40, mature student) and a health visitor that has experience with people like him.
The health visitor more than the counsellor actually has picked me up when I've been questioning everything so I'll pass it on. You should be proud, not ashamed. Your baby is going to know you've done this all on your own and they're going to love you for it.
Some of the benefits:
-your routine on your timeline, your way, without trying to slot him in. My God it's easier.
- 1 on 1 time that in years to come you'll miss so much. Make the most of it, I absolutely love it that we have the time and space to bond without him dictating a thing
- choices. Your own choices to do with baby (outside of the ones he can choose with PR whether he's involved or not). How do you want to bring up baby? You get to choose and plan baby's life your way and make sure they're getting the best in the way you see fit.
It takes time to see and feel the positives and time to feel proud not ashamed but I really hope you get there as it's amazing when the penny drops.
You're so lucky to have just you and baby you know, nobody to influence anything negatively.
Sending you big hugs, please keep your head up high, be proud ❤️