Hi Maven,
Think of it this way, you know when you're at a party or at work and you go to the bathroom and look in the mirror and then see that you got a booger hanging out of your nose? Your first thought is "Why didn't any of my friends tell me?" Yeah, it's embarrassing but you really appreciate it that someone tells you straight up that there's something offensive about you that you're not aware of.
Just tell him like you'd want someone to tell you if you had bad breath. It's not going to make him feel good but it's better then you dreading going near him or anywhere he's been. I'd be mortified if I found out someone stayed away from me because I stunk-I'd be like, Why didn't you just tell me????
Good luck. (((((((Maven))))))))