HI! It is not a matter of serious concern! Brazilian waxing done 2 weeks ago has nothing to do with your present problem of itching and burning sensation in your private parts. If at all you are found to be allergic to the waxing material used or the talc powder used on the hand gloves of the waxer you would have developed immediate allergy in the form of redness, itching, swellings etc but that did not happen. Since you took antibiotics for your sinus infection, the antibiotics as a matter of fact suppress the local immunity in our body including the mouth and the vagina. As a result of suppressed local immunity you might have acquired the fungal infection (Vaginal candidiasis) which can be treated effectively with the use of antifungal creams such as Fluconazole or Miconazole or Nystatine. I hope I tried to solve the problems faced by you following the antibiotic therapy. Have a good time. Regards!