Valtex causing burning penis after intercourse ?

I recently started taking Valtrex, for about 3 weeks now. My boyfriend doesnt know this. I feel as long as im clear of an outbreak and im medicated all should be okay. right? He is now concerned though.Apparently the last few times we have had sex his penis burns really bad after we finish, but only for a short while. Could this be because of the Valtrex i recently started taking? I also often have yeast infections. Could that cause this burning in him? Burning is all that is going on, no other symptoms. Is this even my fault? Could something else be going on with him, health wise?