Am I selfish for wanting child support?

My baby daddy has bad mental health issues and due to that he’s barely seen my son in the last 2 years. He made the decision to stop seeing him, one day just dropped him off and said he needed a break for 2 weeks and never wanted him back. Never even asked how he was doing, just moved on with his life. I’ve basically been doing it on my own for the last 2 years with occasional help from his mom and my own parents. He hasn’t done anything to get better, he doesn’t think he even needs help. Im only able to work 3 days a week so it’s not like I even make much money. I was venting to my family about how it’s not fair I have to do this all on my own and that he just chose to walk away from his own child and that I wanted to put him on child support. Didn’t even say I was going to do it but that I wanted to. My sister got super mean and was saying I was selfish because he has mental health issues. She’s also FULLY aware that he used to abuse me when I was with him, he’s even been arrested for domestic violence against me and still she defends him? Like she was judging women that put absent fathers on child support. I don’t know why, she’s the type of person that virtue signals and likes to feel better than others or more “righteous”. she can’t even take care of an animal and has bought (not even adopted but bought off Craigslist) NINE cats or dogs that she has quickly gotten rid of because she gets bored and realizes she doesn’t want to take care of them. She could never survive having a child and thinks I’m selfish for wanting financial support. am I selfish

@narwhalsarereal he has never been forced into parenthood, he WANTED a kid, and even when he abandoned my son I didn’t try to make him be a parent. Everything that happened was entirely between us, we have never been to court and he never signed his rights away. He has too much pride to ever sign his rights away, he still thinks he’s a father after not seeing his son for 2 years