Suggest Treatment For Strep Throat

Since the beginning of February, I have had a post-nasal drip/sore throat problem. It waxed and waned for about 2 weeks, but when it persisted, I finally went to see my ENT. She didn t see anything that indicated big problems, although she noticed some redness and irritation in my throat and on my vocal cords. She took a throat culture and found slight strep (it must have been slight, because there were no white stripes, fever, etc...). She put me on a 10-day regimen of Cefuroxime. However, I am on my 7th day, and I have noticed NO change. I understand that I still have antibiotics to take, but it is my understanding that symptoms usually disappear in a few days, and the remaining doses are to help kill all of the bacteria. This is vaguely reminiscent of an issue I had nearly 3 years ago - I had a chest/lung infection of some sort, and the amoxycillin I was prescribed did nothing (in fact, the condition got worse towards the end of the treatment). Could I be dealing with resistant bacteria strains? Can people become antibiotic resistant somehow? It also occurs to me that a problem might be my night mouth guard. I use this to help prevent teeth damage due to grinding. I clean it everyday with toothpaste/toothbrush, but it occurs to me that it there is strep bacteria now living on it, I could be reinfecting myself every night. What would be a good way to up the cleaning regimen to kill that bacteria?