AITAH for not telling my ex we had a baby because his mom tried to unalive me?

I, 28F and have an 11-month-old son. This situation is messy and kind of a long, but I really need outside perspectives.

When I was 24, I moved from the Midwest to the South and met a guy I’ll call Keith (25M). We met through streaming, became close friends, eventually dated, and after about a year and a half I moved back down there (from my home m state) and (mistakenly) moved in with him immediately because he said it would be easier than me apartment-hunting from 18 hours away.

He has a daughter, which I knew, but I didn’t know he had full custody until I moved in. I also didn’t realize how intense his relationship with his mom was. She hated me from the jump because I helped her get a remote job (at my company) and she got fired for cussing out a trainer. She blamed me and it never got better.

Once I moved in, she constantly talked badly about me, accused me of “using him,” and would make comments whenever she came over. I always stayed in the room just to avoid conflict.

The breaking point came when she brought over food and I overheard her calling me names and saying I “better not touch her grandbaby’s seafood salad.” My boyfriend defended me and mentioned I’m severely allergic to seafood. She acknowledged that.

Later, she sent over homemade lasagna “for all of us,” which was weird because she knew that’s what I planned to cook that night and she hated me. Something felt off, so before leaving to babysit my brother’s kids, I swapped my plate with Keith’s.

About an hour later, he called me panicking because he found shrimp in his lasagna. I checked the plate I had (originally his) and there was none. I told him what I did. He argued that his mom “would never do that,” so I told him to call her on three-way while I muted myself.

He asked her why the lasagna had shrimp. She claimed it didn’t. When he mentioned the swapped plates, she said, “Why would you let her do that? I wish she hadn’t.” And then said she “didn’t put shrimp in it.” He hung up disappointed, but later tried to downplay it as a “misunderstanding” even though she’d acknowledged my allergy earlier.

That basically ended the relationship for me. We stopped speaking, barely saw each other, and things exploded again when I ran into his mom at the house one day. There was yelling, insults, and a minor physical altercation between me and his sister (they stepped between us). I left and later moved out completely while he wasn’t home.

We stopped talking. He unfriended me everywhere. A few weeks later, I randomly took a pregnancy test and was shocked to learn I was pregnant—I had no symptoms. I decided not to tell him because I genuinely feared having my child around his family, especially a woman who had already tried to give me something she knew could harm me. I moved back home and had a very difficult pregnancy, multiple hospitalizations, and delivered at 35 weeks. My son is healthy now.

Fast forward: I never posted my pregnancy, and I rarely post my child. For his 10-month milestone, I posted a photo on Snapchat. That same night, Keith added me and commented that my son was beautiful. A week later he messaged asking if my son was his. I explained everything that happened and why I kept my distance. He apologized, said he wanted to be involved if the baby was his, and asked for a DNA test. I agreed—with boundaries.

Within an hour, I started getting friend requests from multiple people with his last name. He told me he had told everyone and that “everyone was excited except his mom.” He also said his mom believed I was trying to “put a baby on him” and insisted a DNA test was “mandatory.”

This told me nothing had changed. He still cannot stand up to her, even after everything she did. I told him I no longer wanted a test, didn’t want his involvement, and didn’t want my son anywhere near them.

He flipped out, accused me of being an AH for not telling him I was pregnant, for “taking away his chance” to be in his child’s life, and for “being bitter.” I told him his inability to protect me—even from something seriously dangerous—was the reason I left, and that I refuse to expose my son to a family dynamic like that.

I blocked him. He’s now telling everyone we know that I’m keeping him from “his kid,” but he’s not telling them the real reason why.

So… AITA for not telling him about the pregnancy and for refusing to let him be involved now?

I genuinely don’t know if I’m protecting my son from a toxic family or robbing him of a father out of fear and trauma.