Um, it is extremely RARE to contract HIV/AIDS from 'fingering' someone, no matter what their background is. It is also equally RARE to contract the disease from licking someone's breasts.
It sounds like you are worrying over something that is not likely at all. Just because you have diarrhea doesn't mean you have HIV/AIDS. My advice would be to chug some Pepto Bismol and call it a day.
Obsessive worrying should be followed with a visit to a doctor for anxiety.