Very similar situation here...

I (35m) was friended several years ago a summer love (32m) from HS. We chatted weekly for many years with no major flirting, just friendly talk.

18 months ago something clicked. The fuse was lit and we couldn't get enough of each other. We started texting from good morning to goodnight. We talked about EVERYTHING. We would meet to talk for a few hours and that led to holding hands and cuddling and kissing. We talk on the phone any chance we get. It's a lot.

We say we're best friends, we love each other, etc. I believe it. She has said she would marry me instantly if we were both to become single. We haven't had sex and don't plan to, but have had our emotions push us to the edge when lying together on the couch.

A few times she feels guilty about possibly hurting her husband. He seems emotionally unavailable and takes her for granted. I think that pushed her to me initially. My situation is similar, I love my wife but she no longer wants to work on our marriage, although I've begged her for years. We have similar family structures and are not willing to break those apart yet. We're taking it day to day, but we are getting deeper and deeper. At some point, we'll have to quit or make a move.

When she feels like she should pull away. I just tell her how I feel and ask her what she really wants from our relationship. It becomes very clear to her. I would be very clear exactly how you feel and what you want. The longer it goes on, the deeper you will be.

It's wonderful and frustrating, it's a very tough thing to be part of. However, I feel like it's meant for me/is.

Just my two cents.