He said the most hurtful thing and I don't know if I can heal?

My boyfriend cheated on me with our coworker 2 years ago. It took a lot of healing to move on from it…and he’s now been flirting with the new hire recently. I got upset by this. Things escalated and I said “she’s not going to fuck you” and he replied, “you’d be surprised.” And I blocked him. I’m so miserable that he said that. I’ve been feeling so sad and that comment literally made my stomach drop. I’m so fucking depressed. Why say that to me?

He said the most hurtful thing and I don't know if I can heal?
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