I have a rule that I live by and has served me well my whole life. I do not need a person in my life that can not be up front and honest with the people who trust them. Relationships change, we all know this, but anyone who can not look someone in the eye and honestly address their problems and either work to solve them or end the relationship is a coward. This applies to all genders. You deserve better then that. So if he is interested walk away until he solves his personal issues.
That being said I have worked with mostly men my whole life, and agree with several of the comments above. He may just be a big harmless flirt, I deal with several daily. Call him on if it makes you uncomfortable in anyway.