A mouth differs from an anus in that it is full of nothing but saliva and air. Please reread my initial advice.
Maybe this will help you understand. There is something called theoretical risk. That means, in theory it 'could' happen. BUT IT DOESN'T. To date, no one has ever been documented and proven to get oral sex from giving or receiving oral sex. Therefore, HIV experts around the globe agree that oral sex is ZERO practical risk. Meaning, it just doesn't happen. Therefore, they do not recommend testing for HIV if that is your only risk. You will not get HIV from oral sex. You will not be the first person on the planet to get it that way. The only ways adults get HIV is from unprotected vaginal or anal sex or sharing IV drug needles.
No worries, because you can't get hiv from oral activities. Studies of infected people in an oral sex relationship or who have kissed have proven that the negative partner doesn't get hiv. HIV is effectively instantly dead in air plus also dead in saliva, and the person`s mouth always has those 2 hiv killers in it protecting the negative person from getting hiv via oral activities. Blood and cuts would not be relevant since the hiv has become effectively dead, so you don't have to look for them to be sure that you are safe.
You can read anything on the internet, so I'm not sure why you decided to start googling (for death) but all you need to know is above, so your best option is to move on from googling any more and find a more productive use of your time that does not make you anxious.
There is no reason to see the gp either, unless you keep googling in which case you will still be anxious and he might be able to provide anxiety counseling.