How do I open a BO conversation with my guy?

Ouch! Are you telling me your guy has BO issues and doesn’t know about them? The fact that you like him despite that shows your commitment. My advice: don’t think too much. If you’re honest and helpful, he’ll be able to see that and love you more for wanting him to get better. “Baby, you know there’s a bit of smell coming from you, you need a deo,” is a straightforward way of giving him the message and making it sound like it’s for his good. Do not ever crib or chide; loving partners don’t do that. Once he realises you’re trying to help, he’ll just correct the problem then come back to you another day and ask you ‘Am I smelling OK, today?’ Contrary to belief, men don’t have ego issues with improving themselves.