I understand health anxiety. I have it myself. I was just discussing this last night with a friend of mine who also has this. We both had what felt like a traumatic experience with our health years ago so that now we do things like avoid doctors out of fear. Sigh. But, here's kind of the difference. I can have an almost near panic attack prior to going to the doctor or having a test. But once I do it? I feel great. Then I'm less afraid to go again and get back on track. I just went to a doctor's appointment that I'd put off for a long time yesterday. Feel great! Your situation is a little different. Because . . . you have been to the doctor. You have been told that needle sticks don't cause HIV (injections do, that's why sharing needles is a risk. Needles tips are exposed to air so if they stick you, any virus would be deactivated). You also have had numerous biopsies and the issue you worry about with those has not come to fruition. So, you're given reliable and accurate data that your fear is not your reality. But your anxiety won't let you accept this. Sooo, what is the real issue here? Hiv? Your autoimmune potential disorders? Nope. Anxiety. That's also a disease and that is also greatly impacting you. So, how to overcome the situation? TREAT YOUR ANXIETY. If it is mild, perhaps it will go quickly. But I'd consider therapy with a licensed psychologist. CBT therapy may be great for you. You may also need medication which is for you and the therapist who in a lot of places can not prescribe but work with psychiatrists who can. That can be determined later. But you need help with this as the anxiety is impacting you negatively. My health anxiety feels terrible. I understand how uncomfortable those feelings are. For some, it's enough to make us physically sick. If you view the anxiety as the issue, perhaps you can move past your other health worries.
You said in your response to specialmom that you are thinking of going for an HIV test in 6 weeks, but why? You haven't been exposed. You are showing no symptoms. All a test will do is convince your worried mind that this is real because you're having a test. But it's more of a phobia. The anxiety is real, but the illness you have settled on to obsess about is not.
I work in the DNA/Paternity community, and hear all the time from young women who are obsessively worried that the wrong guy is the dad. One of the things those women will frequently do is repeated DNA tests, one not being enough when you are anxious, apparently. Are they relieved and pleased when they find out the right guy is the baby's dad? No. They are just as anxious as ever, if not more. The prenatal versions of these tests cost almost two thousand dollars, and sometimes the woman will even test more than once (one woman also made the partner she didn't want to be the dad, who had had a vasectomy, test to be sure his vasectomy had worked). Why doesn't the test relieve their worry? (And, in fact, increase it because it's so important-seeming that it gives weight to the worry -- it MUST be legitimate because I'm getting this expensive test!) It doesn't ease their minds because the thing they are anxious about is in fact something else, not paternity. When the mind can't rest due to serious but hard-to-pin-down anxiety, it hates that. So, it thinks of something that is unlikely but specific, and lets the anxiety rest on that. The problem is, solving for that thing doesn't solve the anxiety because that thing is not really the problem.
My guess is, deep down, you really do know you don't have HIV. But it's easier to let the stress settle there than it is to identify some of the more existential worries we have as human beings. That's why the recommendations to deal with the anxiety are so good. If you get to what is really giving you such a dose of anxiety, you will find that your worry about HIV is shown to be straw man that it really is.