You are still being held captive by the jw way of thinking about marriage. "Marriage is forever, no matter what"--thinking! I had a similar experience 10 years into our marriage and we had 2 children at the time. We also married young--19 and 18.
When a woman (or a man) develop romantic interests outside the marriage, there is not much one can do about it. It's not necessarily you, it's the situation. Being young and vital often leads to extra marital relationships. As I look back now, it was my ego that was damaged the most, thinking that I was such a stud. lol....
Anyway, she came back (I also enjoyed a few flings myself during her absence) and we will be celebrating our 50th next year. You never know!
just saying!
eyeuse2badub