I am not sure if my mind has been playing tricks on me, but about 1 week ago I thought I saw a very faint red rash on my penis - lasted a day or so and now gone. Didn't hurt or feel different though. As I said, possibly my mind. However, yesterday I noticed a couple of what only can be described as the tiniest little blackheads on the shaft of my penis. They are minute, probably 1mm big if that, and so small that I wouldn't have noticed them if I wasn't so paranoid and worried about this whole situation. But is this the first sign of something?
By the title of this thread and the anxiety I'm seeing in your post, it seems like you're really making yourself terribly upset about this. It also seems that you're expending a great deal of enegery looking for any minute possibility that will confirm your fears.
Believe it or not, there are very few STDs you're likely to get from receiving oral sex. You can't get HIV from saliva so the person performing would have to be bleeding from the mouth. To date there are no documented cases of that. Chlamydia and gonorrhea are possible but less likely *(information below). Besides, you were given an antibiotic and the symptoms you described are not consistent with these.
The best way to decide what's going on is to have a doctor take a look at you. If he/she can't tell by your symptoms, you can get a reliable test for herpes anytime 12-16 weeks after the possible exposure.
What makes you think your partner had an STD anyway?
*During oral sex, it is possible but unlikely for chlamydia and gonorrhea to be transmitted while performing or receiving fellatio and, even less so, while performing cunnilingus or anilingus. Transmission is not known to occur through receiving cunnilingus or anilingus. Chlamydia is less likely to be transmitted during oral sex because the bacteria that cause chlamydia prefer to target the genital area rather than the throat.