What are the chances that I am pregnant? I'm only 16...?

My partner d onto my back and I believe that some of it may have dripped down onto my bum. I know, it sounds silly. I am really paranoid, so I wiped it off and dumped rubbing alcohol onto my back (hoping that it may kill some of the sperm). Then, I took a shower in a hot water. Is it likely that I am still pregnant? I don't know if the sperm went in between my bum or anything. How long does the sperm live on the skin? How likely is it that I'm pregnant?