It's good that you're seeing a therapist, because that's where you need to be. Hypochondria is a nasty phobia which can rob us of any happiness we find in life. I know this from basically losing over 10 years of my life, time I will never get back, because every minute of every day I had to live with the absolute certainty of my impending death from cancer, brain tumors, strokes, pernicious anemia, Pigeon Breeders Lung (I didn't even own a damn parakeet!) myocardial infarction, Black Lung because I heard about some miners dying from it, even though they lived 2,000 miles away and I'd never even seen a mine..........you get the point.
Please work very, very hard with your therapist to overcome this. And make sure that includes your HIV anxiety. I can give you some quick advice about HIV/AIDS. Get yourself educated about this virus. Learn what is and what isn't a risk, live by those "rules" and you will never need to fear HIV again.
I think it's time you and your partner had a serious discussion. He/she passed on an STD to you. Since YOU didn't have it to pass on, then your "partner" got it somewhere else. Perhaps you have an "open" relationship, but if you do, then using condoms, AT ALL TIMES FOR ANY KIND OF SEX must be an ironclad part of that deal.
Anxiety, which you have an overabundance of now, can definitely cause pain and brain zaps, although the "zaps" are more associated with various medications, they can still happen even if you're not on anything. Yet another topic for your therapist.
Your worry and anxiety are leading you towards depression. I realize I'm sounding like a broken record, but this is where your therapist is REALLY going to come in handy. You've only been to your therapist once! You said it helped "a bit." If you keep going, it's not just going to help, it's going to cure. There's the light at the end of your tunnel.
To find other stories that are very similar to yours, just start reading the posts on this forum. There are a million stories in the naked city, your's is but one.
Please let us know how you're doing, OK?
Peace
Greenlydia