I went to doctor and they gave me amoxicillin for 7 days and i feel better but i still have white patches on throat and one side is still sore. the doctor extended amox for 3 more days. is it normal to have white patches and soreness still?

Yes. If its a virus: Can’t be sure without speaking to you directly but it sounds like you have a viral, not a bacterial, pharyngitis. Amoxicillin (or any antibiotic) will not cure this but these viral infections gradually get better over 1-2 weeks, regardless of the antibiotic. Many viruses can cause “white patches” - EBV, CMV, Adenovirus. If it continues, see your doctor