, It sounds like you have done many different types of tests already. HIV tests taken 6 months after a potential exposure are 99.9 percent accurate. If your HIV tests were taken 6 months post-exposure, you can trust the results. Typically, people may experience a false positive if an HIV test is taken within the first 2 months of a possible exposure; this period of time is called the "window period". However, outside window period, false-positives are rare with HIV test. For more information, see here: https://www.aidsmap.com/about-hiv/false-negative-results-hiv-tests
I saw that you also asked about subtypes. I have some information on the most recent subtype from 2019, which includes that it is detectable by diagnostic testing. HIV tests are rigorous and there are surveillance systems to track old and new strains of the virus, as the article states.
Do you have a doctor you trust to speak to about other things that might cause your stomach symptoms and oral sores? It's totally normal to be nervous; however, it may be helpful to seek more information from your primary care doctor for more insight.
Please keep us posted on how you are doing, and I hope this information can help you. Best, Liz (Team Member)