I was the OW for a year. It was thoughtless and unkind, I know that. I don't know why I did it apart from falling in love with someone else. It became an obsession. I was married and so was he. He for 20+ plus years with grown children, me with an 8 year old son.
Even though I knew it was wrong, I couldn't help myself despite knowing that what I was doing was destructive - I was willing to stumble in the debris of it all. It was an obsession. I thought I'd never be happy again if I wasn't with him.
My ExH caught us (he put spyware on my computer) after I confessed I was in love with someone else. He didn't tell me he'd 'caught me'. Instead, he confronted OM's wife with all the evidence and then they both confronted us separately at a pre-ordained time (after confiscating both our phones) - obviously at our separate homes.
I'd say that m ExH put me in a position that I could not endure (same for OM) and we were both put in the position - which we wanted - of leaving our spouses to be together.
We are now married and have been for three years and we are very happy. We honestly believe that we belong together.
The pain we have caused to our Ex-spouses is unforgivable and I wish our happy and stable marriage had started under better grounds.
I DO NOT think I have created a vacancy for another mistress. The misery we have suffered (also our Ex-partners who have suffered 10 X as much) would never incline me on this path again and I would say the same for my DH. It has caused MISERY for everyone involved. We are lucky in that we are sooo happy together and I don't regret our union at all. I just regret the way that it happened as there is no pride in that.
I never thought it would be this hard. For any OWs or OM out there: think very carefully about what you want. It is a difficult road ahead and nobody apart from your very best friends will accept you.
My DS is very happy though and loves my new DH. My EXH and I get along very well and we share custody 50 / 50 and are better friends now than when we were married.
It's not an easy path and I wouldn't recommend it. For me, it was worth it. I hope that you take some heed from my tale.