Hi. I have had intercourse recently with my GF, she has been my ONLY partner for approximately over a year. I have never encountered any problems during or after intecourse that has affected my health only until recently. Last week we had unprotected intercourse while she was on her menstruation. I ejaculated within the vagina and we stayed together for a few moments longer. After that last time we had intercourse, I have recently felt the tip of my penis (right at the urethra) becoming very sore when touched and turning red. There is a yellowish secretion once in a while and it really hurts when I urinate. I researched a little bit and came to the conclusion that it could be a yeast infection. Can anyone help me out?

Your symptoms (yellowish drainage, painful urination) would be suspicious for - but not in themselves diagnostic of - gonorrhea and a few other STD's. There are other possibilities that are not STD's, so don't leave your GF just yet. You need to see a doctor as soon as possible to get the right diagnosis and the appropriate treatment.

Edit - saw your other post - are you trying to fool us? If you want honest help, you need to be honest with us.