Is this new? If it is, it will probably go away as time passes. Some people are just extremely empathetic. But if this is something that is persisting way too long or is something that is part of your life regularly, then it's time to see a therapist and figure out why you're having such a hard time with your thinking.
HIV isn't hereditary, nor is it something you can catch via air. I worry about things a lot as well, but then I started praying. I've never been a religious person, but after putting my trust in God, my life started changing for the better. I started going to church and prayed more often, and a lot of my worries faded. I'll pray for you.