Sleeping with a married man

This post isn't about me. This is about my younger brother. He told me all of this and I didn't have a whole lot of advice for him so I asked if he could send me what he wants to say and I can post it on here to get him advice. Plz go easy on him. He is only 19 and this all started when he was between 17 and 18.

I made a lot of mistakes and I have a lot of feelings about everything. I graduated high school at 17 and started college last year. About a month into school I asked about started a Gay Straight Alliance since college didn't have one. I got advice on how to start a club and make it official. Not many people came but still some did. One of my Professors complimented me on taking action and started a club based around acceptance in such a conservative town. I'll call him Mr. M. He talked to me a lot about my major and gave me critiques on my essays. He was older. When this started he was 42 and now he's 43. We hung out outside of school and one Dat he said This is a bad idea but do you want to come to my house. He warned me it was a bad idea. So most of this falls on me but I said yes. By then I was 18. And we started having sex. I didn't date guys or girls in high school. I was shy and had bad anxiety. This was my first relationship. The relationship started in October of 2021 and I didn't find out he was married until January of 2022. He's not from America. He's from El Salvador and his wife and kid were back there. He has a daughter my age. He told me him and his wife were separated. I want to say I didn't know he was marries but deep down I think I did. He had a wedding ring on his dresser. I think I just told myself since he hadn't said anything, I don't know. And I made another stupid decision and continued the relationship. After a little time it did seem he started to lose interest. During summer he said he was going home to his wife but it was for their daughter. He didn't really talk to me during the summer. After he came back he pulled away even more. I don't have any classes with him this semester. Friday Mr. M saw me in the hallway but said nothing but did text me we need totalk. I said okay and already knew what this was. I went to his house and he said he was going back to his wife and was going to move her here. I just said okay if that's what you want. He apologized to me and made a joke and said I told you it was a bad idea to get involved with me. But he said he still wanted to be friends. I said okay and that's fine and asked if I wanted to drink. I drank and kept drinking to hide how sad I was and then he started kissing me and I was stupid and we had sex. He got one last fuck in. He still wants to be friends and still hang out but i don't know. I sais that was fine to sound cool and that I'm fine but I'm not fine.. I'm depressed. . And I know I brought this on to myself so it's my fault.