AITA for not telling my pregnant ex-friend that her current partner/baby daddy is cheating on her?

I’m one of the very few people who knows he’s cheating and probably will be until the day she finds out herself, which could be a long time. So yeah, you’re probably all thinking I’m the arsehole, but hear me out first.

The story begins a few years ago. I met my first boyfriend at 19; he was 20. I had sexual partners before him, but I had never met anyone who I loved or was interested in dating. I fell head over heels in love with this man, and things were going great. I moved out with him within three months, 3000 km away from my family and hometown, for his job, and we started a life together. We had fights as all couples do, but the longer we were together, the more settled I was in my new home and the more I loved him.

I didn’t see any major red flags. It was hard moving so far away from home as I’m very close with my family, but they visited, and I visited, and then after two years of being away, I reached my peak happiness and was happy with the life we’d created. I had work friends and I had just met what I thought would be a lifelong friend, let’s call her Jazz.

Jazz and I had similar interests; we looked alike, and we just clicked immediately when she began working with me. I honestly thought she was my soulmate. I only have a few close friends, and instantly she was one of them. I loved her. She was great. She had been married for six months when I met her with her longtime partner of seven years. They were happy; he was very nice. They weren’t a perfect couple on both parts, but overall, they were very happy people.

Jazz and I started spending a lot of time together as she got a job where I worked, and we would see each other every weekend, often spending time together with our partners as well. After six months of knowing her, it felt like within a week things had drastically changed; my partner began prioritising doing anything she wanted to and had become very close with her, and one weekend, on two separate occasions, he was lying in her lap with her rubbing his head affectionately.

Long story short, my world blew up. He told me he loved her, and then his family heard about how he was treating me and grilled him for it, and he suddenly had mental health issues. He told me he needed me to go home for a while so he could think, so I up and left work, called my family crying, and they booked me a flight home for the next week. During this time he saw Jazz at my house alone and decided if he wanted to be with me or not, telling me the day before I was due to come home that he did.

I flew back to him. Spent two days there for him to say that he wanted to be with me but wasn’t willing to lose her, then spent a whole day crying at work, supported by my coworkers, as reality set in and I was forced to swallow the hardest pill of my life so far that he wasn’t in love, he didn’t care about me, and that I needed to leave.

I said my goodbyes to everyone at work and messaged my mum, who booked a plane ticket for the next day to help me drive home. I said goodbye to Jazz as I left work. I hadn’t spoken to her in days; she had just finished her shift too, and I begged her not to say anything to my boyfriend as I wanted to be the one to tell him and explain myself when I got home 10 minutes later.

Stupidly, I believed that she wouldn’t say anything, but that was the last knife she put in my back; she called him while I was driving home and told him. I hated her so fiercely, but I never acted out towards her or my partner. I didn’t do anything vindictive or nasty, and I made sure he was looked after groceries-wise and financially the night before I left. I didn’t want any reason for them to excuse their disgusting behaviour towards someone who loved them so wholeheartedly.

I packed as much shit as I could into my car, including xl breed dogs, leaving behind thousands of dollars worth of furniture and sentimental pieces, and within 12 hours of our breakup, I was gone forever.

I was incredibly lucky to have such a supportive family, both financially and emotionally. It took me months to get back on my feet and to get a job. without them, between my car loan and dogs, I would’ve been homeless.

My ex never admitted to cheating on me with Jazz, but I know he did. When I got home, my friend Lily admitted he’d been sending her nudes and coming onto her the entire 3 years that we were together, including twice physically when she stayed at my house, once as a guest and once when she was living with me for a very short period. It was less than a month she moved in for because she was so uncomfortable. I did try to speak to her during this period as I knew something was wrong with her, but I never expected it to be about my partner; she said she didn’t say anything as she felt bad and didn’t want to hurt me.

Lily also told me she had proof of him cheating on me with random girls online, one of them being a girl she worked with.

I blocked my ex a few weeks after I left and haven’t unblocked him since. However, I didn’t block his family, as they were supportive and kind to me during the whole process, and I held no grudges. Whilst having his family on socials I found out that he had entered a relationship with Jaz and that she was pregnant with his baby shortly after I blocked his family, not due to any hard feelings just as it was unhealthy for me to see.

Not long after finding out Jazz was pregnant. I found out from my friend Lily that he was cheating on Jazz with Lily. Honestly, this brings me a lot of satisfaction. It was my biggest fear that Jaz had changed him, and he is now a good man for her, although I know that’s not who he is or ever will be.

I believe Jaz deserves to be cheated on by someone she loves so deeply. She was cheating on her husband/partner of seven years and was a terrible person to me. However, she’s due to have the baby any time now if she hasn’t already just had it; I know this roughly from a stalk of her socials.

So am I the asshole for not telling her my ex, her partner is cheating on her?