Exfriends told bf our son isn't his. And advice please?

Basically they were mad I saw that they weren't really my friends and I decided to end our friendship. Because of this, they weren't informed of my son's birth or anything else regarding him. So they went to my boyfriends job and told him I cheated on him and our son isn't his.

He came home talking about how he wants a paternity test, how he 'did everything for me', how I ruined his life and he was going to ruin me.

They know my boyfriend has struggled with his mental health and sobriety. He had been doing so well for our son but this ended all of that. He stopped going to his meetings and was way worse than ever before. He had even talked about killing himself. He isn't as bad as he was when this first happened, but he has gone back to drinking and smoking. it's really sad because his AAP counselor had said she was very impressed with how he stopped cold turkey. Anyway, after he saw the holes in their story he realized they were lying to him and we blocked them on social media.

Although this isn't his fault, I can't shake the way he had treated me and our son at that time. And I don't understand why I can't. It's been months, but I can't seem to fully move passed it. There are days where I just want to tell him I can't be with him anymore. Can I get some advice please? I've been with him 6 years btw.