you are asking a bunch of normal people, like you and me... you're not taking a doctors scientific evidence which is what you should do. The tests say your blood is NOT HIV positive so I think you should look into other problems. Get your colon checked. A colonoscopy perhaps?
This is definitely something that would effect your conscience. But you need to see what you did as a mistake, and you need to move on with your life.
How old are you? Is your father bald? If he is, then maybe it's just your time to lose your hair as well. I knew a guy in high school who was going bald, poor guy. As for the constant urination, you may have an enlarged prostate gland which you should have checked!
That girl may have had something, but I'm thinking maybe she gave you a flu, not HIV. The mind is extremely powerful, it can make us well, and it can also make us very sick. You have had the tests done, with everything fine. You need to look at life realistically... now I'm not saying there isn't anything wrong. But you should take into consideration age and stress and what it can do to your mind and body!!
Get your prostate checked, your colon, and KNOW in your mind that you are well. Because chances are, you are. Tell yourself you are well. Good luck to you!!
If you have been tested this many times and come back negative, I hate to say it, but you might be letting guilt over a foolish lapse in judgement ruin your life. We all know that you can think yourself sick, and it sounds to me like you have a strong moral code and that having breached it has upset you greatly. I don't know your spritual calling, but I recommend you speak to a spiritual leader and get yourself straightened out. And get tested for diabetes - you don't have to be overweight to have it...it will cause a lot of the symptoms you are having, especially the extreme thirst and fatigue.