You know, I do like that you are distinguishing that your fears are irrational and based on your internal anxiety. That is a really great start to solving this problem! THIS is what you must focus on. HIV is not a risk (you know this) but anxiety won't let you let it go. So, treat ANXIETY as the disease here. Anxiety is the enemy holding you in bondage to your hiv fears. If you aggressively treat your anxiety, your fears of HIV should lesson. (as will your fears and worries of other things). Please seek help for this. A doctor and a good psychologist are the places to go next! You can show them what you wrote here. Red flag to a doctor and they will want to help you with that overwhelming anxiety creating an urge to hyper focus on HIV and test and take such a toxic medicine for no reason like PEP. Let us know what you think and what your plan is to overcome this. good luck
"I know for a fact the risks are absolutely miniscule. " The advice on the HIV forum was there is zero risk - which is different from miniscule.
I would consider talking to your doctor and explaining how great the fear is so if you get in this situation in future then your doctor will know more about how to deal with it. Perhaps he can even help you through this fear now but if not consider seeing a therapist because suicidal thoughts for no risk indicates that there is something for a therapist to work on.
I can understand how some people like you can't readily get over the idea that virus inside the mouth won't infect, so I am not trying to lecture you. The important issue is that this is a serious HIV phobia that you need to come to grips with if it caused you to lie to your doctor just to get PEP. PEP has potential side effects so it shouldn't be taken as a placebo, especially if your doctor isn't even given a chance to talk you out of it.