First of all, symptoms are NOT indicative of HIV.
Second, you said your "risk" was getting someone's blood in your mouth. This is NOT a risk for HIV and you did not need to test for it. You have tested three times, all negative.........trust the tests!
Testing for OTHER STD's would have been my recommendation. You could have that done now if it will give you some peace of mind.
Since this exposure happened almost 2 YEARS ago, if you HAD been infected, you would definitely know it by now.
If you are still have doubts, see an HIV specialist.
I wish you the best
RubyWitch