The symptoms you describe do not correlate with any STD. The onset of STD symptoms almost never begin within a day or less of exposure. The symptoms you describe are really much more suggestive of bruising or other effect of sex but not an STD. The negative tests you have had would seem to confirm this.
As for the persistent dots, discolorations and occasional testicular pain, I would suggest that, if they bother you, seeing a dermatologist. If not, just let them be and I suspect they will go away by themselves. Unless they persist they are almost certainly not something to worry about. Hope this helps. EWH