Confused

I (late 40’s F) have been single since 2021. Lots of dating but never found someone that 1) shared common interests 2) shared common political views and 3) I was attracted to until very recently. We met and started to date all until I found out that he was tagged in a relationship with another woman on FB.

I naturally confronted him about it and he stated that he had dated her and they had become friends but she had never accepted the “becoming friends” part. She was apparently quite troubled, with children who had very special needs and no dad in the picture, money problems and a drinking problem.

He (male, same age as me) apparently contacted her to tell her about me and to sort of tell her to move on. She did not take it well and basically said she would start drinking again and she needed him.

So he dumped me saying he felt too anxious about the situation and he had to help her get to a better place in life before he dated anyone else, including me.

This is after I have has sex with him three times. Yeah….

Anyway, am I hurt and pissed a little? Yes. Admittedly I recklessly send her a FB message saying “Well congrats he’s all yours girly” sort of snarky but whatever I could have been a lot nastier in that moment.

I didn’t expect her to text me back but she’s like who are you? And I’m like you know who I am etc etc and she denies being told about me. I’m shitting my pants at this point thinking this dude is a dirty liar but when I suggest that I’m so sorry to tell her this, he’s obviously cheated on her and for both of our sakes we need STI testing she gets nasty and is like I REALLY DON’T KNOW YOU GO AWAY

This confuses me because I think if I found out my boyfriend was cheating on me I would be concerned???

Anyways, then he messages me saying I made everything worse and I now see he has blocked me.

What happened? Do I go and get tested? Was he lying the whole time? I just feel sick to my stomach that I was this wrong about everything. Also this was my first relationship after DV that I felt had potential.