Hi Someday maybe,
I'd like to welcome you to bpdfamily. I'm sorry that your toddler had to go through that, poor guy.
I can't believe it took me this long to see that my mother has a mental illness.
Don't be hard on yourself, only a professional can diagnose a mental illness. I grew up with a mentally ill parent, my father isn't BPD, he displays traits of an anxiety disorder of some sort, my home and how I grew up was my benchmark, I didn't have anything else to compare it to, it was normal for me.
You have the right idea with not leaving your S3 with her, maybe things will change when he's older and it won't be permanent. That's sad to hear that it feels like you lost both parents, are you in no contact with her or low contact?