I agree with Snap66 on this. I don't see a future in this relationship, because you're looking for something he can't give. Everyone deserves to feel secure and loved in a relationship, and I don't think this guy is willing to provide these things. You have to wonder why someone would keep a relationship "secret" after so long, and disappear without explanation. There's nothing in what you describe that points to him being a secret agent, so my guess is he may be hiding a lot more than you know. Run, do not walk, away from this person, whatever his diagnosis. You so deserve something better.