Husband had a 3 year affair behind my back.

I discovered my husband had a mistress for 3 years in September. 3 years! I found out because his mistress reached out to me on social media and told me everything! She knew about me the whole time, I had no clue about her. I never thought my husband would even be capable of doing this to me. Anyway, I put him out and told him I was divorcing him. I ended up losing a very close family member about 2 weeks after I put him out. In a vulnerable state, I allowed him to come back home and try reconciliation. I was extremely depressed and spiraling. Reconciliation seemed to be going well. He was home a lot more. We were going on a lot of dates, and things seemed to be going well. Fast forward to the beginning of February, the same damn mistress reached out to me and told me they actually never stopped messing around! He would go over to her house and screw her, then come home to me as if nothing happened! I was crushed! This second discovery seemed to hurt worse than the first time. He literally was cheating on me while I was grieving and struggling mentally. I told him to leave and that I was done for good. I told him I was filing for divorce. Now, this is where I want to know if IATAH. Last week, while I was sleeping, my husband came in, took my phone, and went through it. I had no idea. He saw me messaging with an old male coworker of mine who was recently divorced. I was asking him for advice and basically venting. We met up for coffee twice. No romantic feelings are involved at all. Now my husband is saying that I betrayed him, and he can't believe I would do that and is now refusing to speak to me at all. He says that I cheated on him. We have been married 11 years, and I have NEVER cheated on him! I can't stand cheaters. He has told his mother that I cheated on him, and now she's harassing me. So please give me your honest opinion, AITAH?

Update: I noticed a few comments suggesting that I change the locks. I didn't know if I could or not. Am I allowed to change the locks even though we are still legally married and the house is shared property? Most of his belongings are gone, but he still gets mail here, and we share 2 sons together.