Not dating related specifically, but just really needing some overall support.

Long story short, my ex and I recently divorced after being separated for about a year. During our rocky times, I was living in a different state for my job but would come home every three months to see him and our three kids. On those visits home, I started becoming very suspicious of him and my "best friends" relationship. I directly asked both, multiple times, about my concerns and was essentially gaslit for a year being made to feel crazy. I was told it was all in my head, I was just insecure, nothing was happening.

Fast forward to now, her and I are no longer friends because I found messages between the two of them that proved my suspicions. I didn't find anything concrete but of what messages weren't deleted, I saw her telling him she had dreams about him and missed him. While her and I were out together for New Years Eve, she was messaging him that she would rather be with him. I never directly confronted her with the evidence, I just told her I knew and I was done. Again, still just making me feel crazy for everything.

I cam home last night after my ex had them for the weekend. I knew they had all gone to her house because the kids are best friends. Out of the blue my 9 year old son came up to me and "mommy, I think daddy and Ms "B" are secretly dating because they were flirting really bad all weekend. They thought I was in the backyard but I heard them."

In one way, I just want to scream VINDICATION! Because I KNOW I am not crazy. I knew my intuition was right. But in the other way, my heart just really hurts. I just want them to own their shit. Tell me. Respect me enough to not make me look like a fool. And even more so, I don't give a shit what he does in his private time, but I sure as hell care when my kids are involved and I have to be put into conversations like that. My response to him was that he should ask his dad. He asked me if I would be upset if they were dating and I told him that my only concern as their mom is that whoever he chooses for a partner treats them well. I know Ms "B" loves them and cares for them and that is all that matters to me.

I feel like I get over one hump of this emotional roller coaster and then, BAM, down I go again. I just need help on how to stay sane through all of this because I'm freaking exhausted trying to be strong.