Hi T.,
When our kids struggle, it can raise so many fears and test our feelings of helplessness. Try to push past these and remember that you know him best; and are his best shot at helping him navigate his way.
Eight grade is tough. He may feel like king of the hill now but high school is looming on his horizon. Who are his friends? How does he feel about your fiance? How well do they know each other? Do you both agree on parenting?
Take him out to dinner, just the two of you. I do this with my 19 year old. You will be surprised what a change in environment will do. He has you all to himself, no distractions, he may feel safe enough to open up. There is much change on his horizon, knowing he is still your #1 is critical for him.
I made sports a requirement for my kids. If he isn't involved now, recommend it - strongly! He will be part of a team, and he will need to belong somewhere, and I can think of no better spot than on a team! He will belong, make friends, will need to work REAL hard, and it will occupy a tremendous part of his time. He'll be a part of something bigger than himself.
This is a trying time as parents, it is tough on them too. You'll find your way to him, try the dinner thing.
L.