Melodious,
Welcome to Sober Recovery. This is a terrific board, and one which you will find sympatico with.
You have asked for help, but I'm not sure what it is exactly you ARE asking. I think if you keep coming here, reading and posting, you will learn a lot. Getting some reading material by Melody Beattie, and going to Al-anon or Nar-anon meetings will also be helpful.
You said you would not be so concerned if this would not affect your health? What is it that you mean by that? Do you feel you are in physical or emotional danger? Health consequences such as communicable disease?
Has he realized that you found the syringe?