MEN: Tell me how I can be sure a guy IS a sneaky snake in the grass!!!!?

I broke up with my boyfriend after a full year of suspicious activity with his laptop, cell phone and "outtings" to do "odd jobs" for friends/family. No details I want to share except that I always had a gut feeling he wasn't on the level with me and I was sick of him telling me I was just a distrustful jealous woman. He is computer savvy and I have a hunch that he has a secret "minute" phone as well. I must sound paranoid. Ha! Actually, I am sane and rational but have ABSOLUTELY no need for this man whatsoever except for love, companionship and sex and if he isn't worthy of me then I don't want him. He says he loves me with all his heart and soul and that he wants me back. He has a point that I have no proof to back up my suspicions but....I'm convinced he has been too damn good at hiding the evidence. any advise to catch a sneaky man on the prowl or at his game is welcomed.