Hi. I also suffer from this time to time. I actually got my blood drawn to test for hiv and hep a few days ago and the same exact thought went into my mind. Thats anxiety/OCD for ya. While anything could be possible, i just keep telling myself that this is highly unlikely. The person drawing your blood wouldn't reuse a needle because it is their job for patient safety. If youre really worried you can buy those oral swab tests at the store that check for hiv, but i believe the window period for those is 3 months. good luck to us.
There is definitely a lot of health anxiety and around the area of contracting HIV. I wonder why. We know so much about HIV now. How it is transmitted, that it is treatable and that dying of HIV is not that likely anymore. I wonder if it sometimes comes from shame and guilt for the sexual encounters people have had. But it definitely turns into a cycle of anxiety that ruins people's ability to function, I've noticed.