OCD about diseases is real common man, especially concerning diseases like the ones you have mentioned. I can assure you that you arent at risk. Like you said, the pathogens wouldnt have survived on the pipe or the dollar bills. HIV in particular is extremely fragile, it dies quickly when exposed to the atmosphere (literally seconds) and so does the Hepatitis virus. They need the body to survive. They are actually difficult diseases to catch. They are much more likely to be passed on through sexual contact, and even then contact with an infected person doesnt alwasy result in infection. In the extreme unlikelihood (and I do mean extreme) there WERE pathogens you came into contact with, no way would they have been in sufficient strength to infect you. The only way you could get infected from the pipe/bill if is there was SIGNIFICANT fresh blood from an infected person on them and it somehow found your way directly into your bloodstream within a matter of seconds. So you've got nothing to worry about. And I dont see any reason for you to get tested. You'd have to wait at least 3 months for an HIV test alone, so dont put yourself through that when it isnt necessary.

To put your mind at rest in future, dont share pipes, dollar bills, needles, whatever with anyone. I think I should mention that the use of drugs with any sort of OCD or anxiety will make the problem worse. Give your self a break dude if the obsessions are that much of a problem.

I can relate, because I had the HIV fears too. I went through the hell of getting tested, only to find out that I was ok.

Steve