I suppose you could have had mono (caused by EBV). CMV with those symptoms seems far less likely. You could have also had influenza. The genital lesion is likely the thing that is throwing you off.
Have you considered asking the person with whom you had sex to be tested for herpes? Also was this person the giver of oral sex to you? If yes, then I think you would also need to think a little more seriously about HSV 1 which is missed 1-2 times out of 10 times the routine screening test is done. You may wish to arrange for a herpes western blot for that. However, if you did not receive oral sex from this person, then HSV 1 genital infection is unlikely unless you may have acquired it some other time and it just showed up after this encounter. Lots of “ifs” I know. Even if you had a positive HSV 1 test on the western blot, it would no necessarily indicate that you had genital HSV 1 infection. So as you can see, it is complicated.
It would not be possible to find out what you had at this point by antibody testing for EBV or CMV.
Except for definitely ruling out herpes, I don’t think you should get too hung up on finding out what caused your symptoms. Many people get sick and get better and never know what caused their illness.
If you are asking me whether you should have been playing sports, I don’t really know.