@Kygirl,
... or you could ask your husband and get the real scoop.
Are you asking us to validate your suspicions? We have no idea. You haven't given enough information. Maybe it's completely innocent.
Consider a case in point. I am a woman and have worked with men in every single job I have ever had. I have kept in touch with some of them. I don't tell my husband about every single little PM or email that passes between me and these guys. Why? Because I'm not cheating on him. Why doesn't my husband get jealous and think I'm hiding something? Because he trusts me and knows I'm not cheating on him.
So unless you've got some other reason to suspect him, other than contact, it's more likely to be the latter. But ask! What the hell.
Oh, and another thing. If there's no other evidence of misbehavior, then I suggest counseling, so that you can figure out why you're suspicious of someone who doesn't deserve it. A life full of unjustified jealousy is horrible for the person being accused, and can drive them away, thereby becoming a self-fulfilling prophecy.