Biggest red flag at the start that now makes you feel like a total idiot?

We were hooking up for a while before we got into a relationship. On one night, after sex, completely out of nowhere her face became the picture of anger and she started yelling “You’re nothing!” over and over. I left immediately; never seen crazy like that before. Whilst driving home she was calling and texting me constantly, I ignored. Get home- fuck! I left my keys there. Drive back. Get lots of apologies, end up back in bed (yeah I probably wanted that the whole time). “Sorry about I that, I did it to my ex a couple of times too”. Start watching a movie on her laptop. All these texts appear on the screen from several different guys: “Hey, you called?” “Hey did you just text?” Etc.

I ended up spending over a year of my life total with this girl, moved in with her, and was trying for a kid. What the fuck is wrong with me?