HIV from a dirty bathroom?

I know this sounds crazy, but I went to a REALLY DISGUSTINGLY dirty bathroom a few months ago out in the Mission in San Francisco (if you didn’t know, the Mission is a very poor neighborhood). Anyways, I went to go pee, and though I didn’t sit on the toilet seat, my thong touched the bottom of the toilet. I then put my underwear back on, and I may have had a cut on my …who knows (sorry to get graphic, btw). But the fabric of my underwear did touch my just seconds after touching the toilet seat. What are the chances I could have contracted HIV? If there was fresh HIV infected fluids on the bottom of the seat, wouldn’t I have been able to have contracted it that way? Also, there are a couple of times I can recall having changed tampons in some pretty dirty gas stations, and in some pretty nasty parts of town, in San Francisco (a city that admittedly has a rather large HIV-infected population). The tampon never fell to the ground, but I did touch doors/handles and then didn’t wash my hands before inserting the tampon. How effing stupid do I have to be? I’m really tripping out…HELP!!!