I understand your concerns but there is no reason to be worried .The symptoms that you are describing such as pain at the tip of the penis and burning sensation while passing urine is probably due to a urinary tract infection. The main causative organism is Ecoli and presents with the above-mentioned features. However the pain at the tip of penis could also be due to constant rubbing of the penis that has irritated it or due to irritation of the urethra. It is highly unlikely that you have had HIV or other STD diseases since there was no direct contact. Generally in HIV it takes at least a month for the symptoms to show up and till then they are symptom free. If it is a yeast infection, then you will present with itching, red spots of the penis, passing a thick curdy white discharge. Since you don't have the above-mentioned symptoms it is highly likely that it could be a yeast infection. All your blood reports are also normal. I would suggest you to use an antibiotic like Tablet Cipro 500mg twice a day after food for 5 days. IF the symptoms does not subside after a week then you could consult your doctor.