TIFU by sleeping with my workout partner after my husband told me to

Hi I (32yo female) and my Husband, (34yo male) are having the biggest fight of our lives. My husband and I have been together for 8 years and married for 5, things were mostly fine, we occasionally fought but it was never anything we couldn't work through. He is the sweetest guy on this earth and I want desperately to go back home but he kicked me out for cheating. on him Before I go further, It's important to know that my husband and I are DINKs (dual income no kids), so we have the money for 2-3 vacations a year. On these vacations we occaisonaly have attended swingers parties, and sometimes bring in a third (always a woman). This is fun for us and spices things up, but it was something we have only done together.

My friend Chris and I have known each other for a few years, we met at our office's onsite rec center while working out. We both work at a big tech company so I never had seen him before, but we instantly hit it off and became friends. I'll admit it, he is an attractive guy, but I never had any intention of being more than friends with him. He has a wife too, so nothing could ever happen, and it was so nice to finally have a workout partner. Here is where the problem starts, I had an allergic reaction at work one day and called him to take me to the hospital. I didn't want to call an ambulance and my husband's job doesn't allow him to have his personal phone during the day, so I called Chris to take me. I feel guilty saying it, but something about how concernced he was, how he grabbed my arm, and he looked at me drove me crazy... if you know what I mean. He had to go home eventually and a little later my husband picked me up and we went home.

I could not stop thinking about Chris after this. I've read crushes are natural and will fade in and out, so I tried to ignore it. I always knew he was conventionally attractive but woah. A few days later I felt good enough to get back in the gym and this is when he dropped a bombshell on me. Apparently he and his wife are getting divorced!! I had no idea that they had any issues. I made sure he was okay, and he said he was. They both lost feelings awhile ago and he said he was honestly excited to be free again. and find someone fun.

That sentance played over and over again in my mind for the next few days. I felt really shameful about it but it wouldn't stop. Not wanting to keep it buried, I decided to tell my husband about my thoughts. To my surprise he said it turned him on. He said I could pursue sleeping with Chris if I wanted but with some rules. He said he didn't want to meet Chris and didn't want him in our house but otherwise didn't say anything.

So I did it, after our next gym session I asked Chris what he meant by 'finding someone fun'. He was hesitant, but told me that he was looking for someone to casually go on dates with and maybe have some benefits with. I jokingly offered "my services" to him but he could see I wasn't really joking. He pressed me and I told him about the al with my husband. Chris said he had always found me attractive and asked me to go grab a drink. I texted my husband that I was grabbing drinks with a friend. Long story short we never made it to the bar, we had sex in his car, then in his kitchen and then in his bed . He was f-ing fantastic I can't believe it, it all happened so quickly. I haven't had that much fun in a long time. Around 10:30pm he called me a cab and I went to get my car from work and then headed home to crawl in bed with my husband.

My husband works early shifts, he gets up around 4am so I figured he would be in bed already, but he was up... He came to the door and asked where I'd been. I told him I was with Chris and he instantly broke down crying. I was so confused, I have never seen him like this, and I thought that he would've been happy for me. I tried to comfort him but he wasn't having it and he slammed the bedroom door in my face. An hour later he came out, half composed, with a packed bag full of my clothes. He very sternly told me to leave, that he couldn't believe I cheated on him. I am so distraught. Apparently it was a test this entire time, he said he couldn't believe I actually did it and that he wants a divorce.

I haven't cried this much ever and I don't know what to do. All our friends have kids and I didn't want to bother, so I drove to Chris's house. I had no where else to go. I am sitting in my car writing this deciding whether or not I should go inside. I feel so incredibly guilty and stupid. I wish I could take it all back I never wanted to hurt my husband. Is this my fault? He has never been jealous, we have awung mulltiple times and above all he told me to sleep with Chris.

TL;DR
My husband said it was okay to sleep with my workout partner. So I did, and apparenty it was a test and now he wants a divorce.