Hi I'm 18 and sexually active, and a couple months ago I had unprotected sex with a girl. I already know it was a mistake so don't bother telling me. A couple days after we had sex a red, stinging pain, itchy spot appeared under my penis crown on the shaft and I had pain during urination. I went to the dermatologist who said it was unknown to him but did a few Q-tip tests anyway. He confirmed that the tests all came back negative so i doubt it's an STD. Anyway now the red spot has disappeared and turned into a purple, slightly inflated patch that is glossy and seems to be spreading. It spread to the right side of the penis shaft maybe half a centimeter under the penis head where another red glossy spot has just appeared, but this time around barely have any urination pain and it's only mildly itchy, not painful in any way. could this be a yeast infection?