My boyfriend cheated on me and lied to my face. How can I cope with betrayal?

Here’s just my rant/how I feel right now. I have to share it with someone. This is the man who I’m married to. I will refer to him as boyfriend because the marriage wasn’t a “real” marriage, it was an agreement so that we live together in his country. You may have seen my questions related to him. But here’s the last one. It’s over.

We had been talking for two months. He flew to see me, stayed over, and we had a week of intense connection, traveling and many sexual experiences. When he left, he texted me instantly saying he wants to see me again and that it was a lovely time, he didn’t feel this way for a long time with anyone and never cried listening to classical music with a girl (lol).
We texted every day since he left. He was attending a horse racing event for a week that week and sending me many videos from it. Exactly 5 days after he left, we made plans to see each other again in two weeks. That same night he slept with a random girl whom he claims he doesn’t find attractive or like. The details: they had sex twice, once in the bathroom, once in the bedroom where she got on top of him. They didn’t use protection, and he came inside her.
I’d of course been oblivious to any of this. The next day, strangely enough, I wanted to know if he is seeing or sleeping with other girls (since we live a bit far but we will be seeing each other, so I wanted to know this for myself.) he texted me saying he only sees one girl at a time, and that I’m the last person he slept with. I told him me too, and said I only care for honesty in partners, more than anything. He continued to lie.
We went on many holidays, he met my parents, we spent 6 months living together around the world. I felt like he was the person I will marry. Never felt this before with anyone. He said he felt the same.
Occasionally though, he would lie about certain things like never having had sex while on drugs, or about his past and relationships. He told me that that week of horse races, after we spent our first week together, he didn’t even want to kiss anyone. He only talked to a girl at a bar, but then left and didn’t go back to see her, which he said means “I must’ve just been infatuated with you so much that I didn’t care to go back and talk to her more…” We would have discussions where I tell him how much I value honesty after or before he would lie. He would tell me there is absolutely nothing else left that I don’t know, that he told me everything truthfully.
It didn’t even cross my mind that he involved another girl in our relationship. That would be absolute worst thing, and the last thing in my mind. He was just not THAT… I trusted he didn’t do THAT. I was the last person he slept with, after all.
6 months later, which is two days ago, after an argument he confessed to me that he slept with someone on the Saturday of race week. I asked the details, and he told me them. He said she left her stuff at his. So after two months, he talked to her and gave her her stuff back. This was when we’d gotten serious. This was the week after he met my parents. When I thought he was at work, he was walking to the girl he slept with and giving her back her rings.
I started to shake. I was in denial. My had an anxiety attack. Now I’m a mess. I feel everything was a lie. How dare he? How dare he do it, but also how dare he lie about it for such a long time. How dare it be unprotected, when he knew I wanted to do unprotected with him on our next trip and asked him to get a test. He said he hadn’t had unprotected sex in 5 months. How dare he risk my health. How dare he lie to my face, wake up next to me every day and go to bed. I felt safe lying in bed with him. I was a fool. I was living in a different reality. I now question my sanity—I don’t know how to cope with this. I’m afraid of people even more so. I have never been this sad my entire life. I can’t sleep at all. I shake thinking about that night, thinking of him sleeping with a girl and me being oblivious he involved anyone else. He lied. I asked. He lied. He lied. He is a liar. I never knew the person I thought I was closest to.

Now I am married to him though. So its not very easy to just stop.