Should I tell my husband that I have been in contact with a man from past?

The man from my past is the only other guy that I have slept with besides my husband. This other man and I never really broke off our relationship we went to school together and when we both graduated, being from different states we didn't officially end it. It's been 15 years since I've seen or heard from him. I just want to be honest with my husband and tell him the truth but I'm scared that he'll think something has happened. I still haven't seen this guy, he's stil in a different state but he found me through facebook, so we've been chatting online and this about it.