We all have to do what we feel is right and if you having this test will make you feel better than absolutely go for it! But if in the mean time you are having anxiety, give the breathing and meditation a try.
I have been in your shoes only my "exposure" was in the work environment. I didn't trust the people around me to be taking the right precautions. I ended up right where you are. I got past it and you will to.
I will go for a test. I will feel much better after. I have a baby 6 months old and this is making me feel not to good. I feel big responsability on my shoulders.
The HIV prevention forum is right, your chance is pretty much 0. The problem with internet searches is if you do enough of them, you are going to find one that says what you don't want to hear. So while the internet is good for some things, it isn't always great for people who are in the middle of an obsessive irrational thought process.
What do you think is going to give you relief from these irrational thoughts?
If you want to get tested just for peace of mind, even though you don't need to, you can get tested at 4 weeks post "exposure". Exposure is in quotes because in my mind you didn't have one. You don't want to do it sooner.
If this obsession is going to start affecting your daily life, then the best thing to do is to go and see a psychologist who can treat your OCD and help you learn ways to alleviate the anxiety these thoughts are causing.
I know it is hard once you get in the cycle of irrational thinking but you need to just say STOP in your head and picture yourself pulling a handle down. Every time you have a negative thought about this, replace it with a positive one such as "statistically my chances are 0." There is also a breathing technique that can help you to calm down. You breathe in through your nose, hold it for 5 seconds and count this out in your head, and then let it all out through your mouth. Do this repeatedly until you are calmer. There are also meditation videos on the web which are also helpful.
Let me know how you are doing and what you decide to do.