Sorry to hear this...Like you I started dating my H when I was 15 and we married when I was 18...and while we did save our marriage after a 2 year seperation I learned that after a certain point the love I was holding on to was the IDEA of US..I was the one that file for divorce...the first time I chickened out and had him go to court with me to call it off...a few months later with NO contact from him I filed again...because at that time I knew I couldn't trust him...I saw no moves from him to earn that trust and I knew that my love was not enough...and I didn't want to put all of my love into an empty pot.
Long story short...before the next divorce was to be final H moved back to town after he said he would never do that...he said he wanted to be closer to our son...but he started seeing me and taking me out...it was then that I started to see the changes in him...granted I took him back a little too soon...I was able to weather the alcohol rehab and depression (that he was forced to admit to without alcohol) and he got the help he needed...then we were able to rebuild...
I can tell you though, had he not moved back to town, had he not made the effort to love me again I was truly ready to end the whole thing...yes, he was my sweetheart and yes I pictured us forever being partners and being in love...the dream was the hardest thing to give up...but the second time I was ready...
You never know what the H's will do...but I would say with yours having the same OW...for this long...I would call it a day and let him figure it out without me...if it rocks the boat that think will always be in the safe harbor waiting for them then you can always go from there...but it it doesn't...you have your answer and you can move on...find new dreams...build a new life...make your own way...
It is hard to imagine, I know...when you grow up with someone to even imagine that they could ever do this to you...but the reality must be faced...and you need to resolve this within yourself.