Wow- You have every reason to be concerned. I think acyclovir is the generic of Valtrex, and if he says it's for a virus from a bone spur in his hand he is probably not telling you the truth.
The only other virus I saw that Valtrex treats is the cytomegalovirus which is basically the same thing as herpes.
Follow your instincts. If you think he's hiding something, then chances are he is and if he is being dishonest with you, then you need to stop the madness now. A relationship is built on trust and if you can't trust him, he should be out the door- especially if he is/has potentially put you at risk of contracting and STD.
Good Luck, and I do hope he doesn't have an STD. Please keep us informed.