Three months ago, I had unprotected vaginal and oral sex with my girlfriend. She told me that she had no std's and that she had only had sex with one other person besides me. After we broke up, two weeks later I had vaginal and oral sex with another girl but this time I wore a condom during vaginal sex. This girl also said that she has not std's. It has been one week since we had sex but over the past few days, I've been having this strange penis discomfort that comes and goes. It is a slight burning sensation that is centered around the tip and the upper part of the shaft. I've also found myself urinating more frequent then usual although the pain is not heightened when I do. There are no signs of redness or tenderness. I also got HIV test yesterday that came back negative. My question is, are these signs of an std, uti, post sexual intercourse pain or just anxiety?