Well, that is great that you tested negative for HIV. You took the best test possible and I hope you realize you are clear from it. Depending on how much anxiety you have it can lower your immune system. Have you been tested for diabetes? It sound your immunity is low for some reason. Do you drink a lot of alcohol? Also, eating a lot of sugar? Have you had a complete blood count? Other than these things I would talk to your doctor about why.
Well, firstly your risk was very low to start with. The best time to test for HIV is about 28 days to 30 days. If you have dry mouth that can be a cause of yeast also corticosteroids for asthma can do that. Some other medications could cause yeast too So, there may be something else going on. If you are still concerned talk to your doctor about the results.