Dude, you had no risk, it is impossible to contract the virus through Oral. and yes, 4 month tests are conclusive
As an adult, the only risks for HIV are:
1) having unprotected, penetrative vaginal or anal sex, or
2) sharing IV drug needles with other IV drug users.
You had ZERO RISK for HIV. No one has ever been infected with HIV from receiving oral sex, and you will not be the first. You did not need any tests, and you definitely do not need any more tests. Forget about this event and move on.