As I said in my last posts, I had sex about two weeks ago this Friday and I used a condom (it did not break and held strong

) however, not 2 days later I started to get some burning when I went to the bathroom (not a lot but noticeable) and my genitals started to hurt a little off and on during the day. I hoped it was perhaps an allergic reaction to the condom but after a week of washing and cleaning the symptoms continued. This encounter on Friday was the first time and I was sure not to get my penis any where near her without the condom on tight.
So...Last Monday I went to the doctor and he did a penal swab (I don’t know what to call it) and a few other tests. I told him the details and asked him what it could be..such as herpes, trech, chlamydia or gonorrhea etc. This is what worries me.. He said that he does not think it is herpes since he has never heard of herpes giving any symptoms in 2 days (but he did not rule it out) but he asked me if I had had any urinary discharges and I had not had any discharge nor have I had any scabs or bumps. He seemed a little puzzled by it.
He gave me something called (not sure if I spelled it right) doxicycline that I am to take for 7 days. Now, I have been on the medication for about 3 days now and I feel like I am a little better but I still have some presser in my genital area and my penis still seems a little tender off and on through the day.
Do any of you have any clues on what this could be and do you know what doxicycline is and what it treats. Any help you give will be much appreciated.