I should add That this was about 4 weeks ago, had a sore throat after, followed by the cough but tool antibiotics for 10 days. Doctor didn't much look at it, just gave me the prescription.
Did you give or receive the oral sex?
If you received it, any infection you got would cause genital symptoms. If you gave, you could have oral symptoms, but there isn't an STD that gives you symptoms of an upper respiratory infection. You should go back to your doctor as the antibiotic didn't work.
Did you kiss this person? You could have gotten the flu, any number of respiratory infections, strep throat, mono/glandular fever - it's a long and varied list.
Would amoxicilian knock out anything bacterial that would be causing the headaches? I have some joint pain too, it's been a month since exposure.