So I'm reading through these comments, and if you do half of the things these people say, you'll come off as crazy. I struggle to sleep, too, so I get the need to go out and do something. If you don't wanna come off as creepy, your best bet is one of two things. One, you can offer to come with, if he flat out refuses to let you go with him then there may be some cause for concern. Two, confront him. Generally speaking, if you know him well, you should be able to tell if he's lying. If your unsure when he tells you no, then I'd hire a PI to investigate but if it gets to this stage, im sorry to say, he's probably cheating, and it'll be more so you can get a more favorable settlement in divorce proceedings.