You were prescribed the Amoxycillin for a bacterial infection. As you have now got other symptoms, it is highly likely that the antibiotic is not the right one for the bacteria that you have, or you have a viral infection.
Allergies to Amoxycillin usually present themselves with a body rash.
Make an appointment to see your doctor again, so that he can take a swab from the throat. If it is still a bacterial infection, the Amoxycillin may not be the right antibiotic to treat the bacteria that is causing your problem.
Because taking antibiotics kills off the bad bacteria as well as the good bacteria, the body can start to get a fungal infection either in the genital area and/or the mouth. A swab taken from your throat and mouth would indicate if it is a viral, bacterial or fungal problem that you have.
For a fungal mouth problem, the doctor would prescribe either Nystatin drops, or Daktarin gel for oral use. You can buy Daktarin without a prescription, but I would wait until you get the results of your swab.
I feel that it is highly likely that you now have a virus and if this is the case, unfortunately, no antibiotic will help. You will have to be patient, take pain relief as directed on the packet, drink plenty of warm drinks - honey and lemon is nice and soothing. Have medicated throat lozenges and use those as directed on the packet. You can gargle your throat with salty water and spit it out. You can also purchase from the big supermarkets and from the pharmacy a spray to ease the sore throat.
Do make sure that you drink plenty of fluids, but avoid alcohol, dairy and milk products while you are unwell. These can encourage the formation of congestion.
For the sinus problem, do steam inhalations. Boil up a kettleful of water (taking care not to get scalded) and pour this into a bowl. Put in some Vick or Olbas Oil, or any menthol drops you like. Bend your head over the bowl and cover your head and bowl with a towel. Breathe in the steam through your nose and out through your mouth. Do this 4 times a day if you can and for a duration of 10 minutes each time. This also helps if you have congestion in your ear and Eustachian tube.
Wishing you a speedy recovery.
Appears that you might be having an allergic reaction to the drug, I suggest calling you doctor as soon as possible and alerting him to the new symptoms, it also would be a good idea to tell the pharmacist as well.
It's possible you have a fungal infection in your throat from taking the antibiotics. Notify your doctor and let him know of the change of symptoms and he/she might prescribe another medication to take for a fungal infection (which is different from a bacterial or viral infection).
Other things you an do while on antibiotics is to eat or take probiotics, like yogurt with live cultures (look at the label for a list of the actual live cultures) or take an oral probiotic like Florastor. Probiotics are "good" bacteria, while the antibiotics get rid of the "bad" bacteria. When taking a probiotic, wait at least 1 - 2 hours before or after taking the antibiotic.
Let us know how you do.
Sometimes it does get worse before it gets better also have you had your teeth checked out could possibly be an abscessed or infected tooth causing the sinus problems