In my opinion you need to go back to the doctor, especially if you've still go tthe sores in your throat and the fever (even low grade). It could be you need a stronger antibiotic and the reason you tested negative for the strep could be that it was too early in the illness to register. I had this happen the winter before last. I had a horrible sore throat, fever, body aches, etc., and went to the doc - was tested for strep and was negative, but like you, because ol the symptoms, was put on antibiotics. They did not help and I continued to get worse. Returned to doc four days later and they retested me for strep and this time it came up positive and when I asked why it didn't show before, that was what they told me - it could have been too early in the illness to register. Anyway - went through trial and error with 4-5 different antibiotics before we finally found one that helped!
Don't worry - you are NOT being a baby - any time a sore throat intereferes with sleep, breathing, eating, drinking - it DEFINITELY needs to be investigated.
I hope you feel better!