Nouriya, I'm in a similar boat. I have a LDR with my secondary partner and both of us are married to other people. We have four kids among us, and we own homes and are very settled in our communities. I only get to see him every 2-4 months, depending on what is going on. Although we have only been together for ten months (and that is if you count virtual friendship, which is how we started), I see him as a life partner and I know he sees me the same way. I just don't know how to get to happily ever after from what we have now. I am completely committed to my husband and my OSO is completely committed to his wife. I haven't even dared to fantasize about living with him but living in the same town would sure be nice.
What bothers me the most about being a secondary is having very little input in terms of who else my OSO dates. He dated someone local over the summer, who sounded very nice to me, and I was supportive. It didn't work out, and now he is interested in someone new. I have seen this person's profile on a kink site and I think she sounds like a sociopath. In addition, I am very uneasy about any partner of mine being potentially the sub in a D/s relationship (new woman is a domme), after having a very bad experience with a domme metamour in the past, who booted me out of a long-term relationship with someone I loved very much.
(I hadn't even known my OSO was interested in kink until he told me about this new woman, we have always been vanilla and he seemed happy with that. I could have easily played that way in our relationship, I have some experience with that, but he never asked.)
Anyway OSO listened politely to my concerns, then told me he could take care of himself and not to worry. I dropped the issue, but I hate not having more input than that. If I was his wife, I know I would.