[Aliantha]

If I were in your position, I'd bring the subject up very plainly. If you've been through counselling etc, then surely he must have some understanding of how your mind and emotions work if not just from being married to you for that length of time. Simply say you were suspicious, so you snooped. Big deal. If he's got nothing to hide he surely will understand. If he does, well, only you can know what to do from there.

I wish you well. It's a horrible feeling when you suspect your spouse of cheating.