What should i do about a sore throat and white patches at the back of my throat?

Consult a doctor: You have have strep throat, this needs to be treated with antibiotics. For sore throats that are not strep, you can treat at home with pain relieving throat sprays/lozenges and gargling warm salt water. Consult a physician for a rapid strep test to see if antibiotics are needed.

Needs treatment: This seems to be likely a case of oral thrush or pharyngitis. You need an evaluation and appropriate treatment.

See Doctor: Could be strep. But not absolutely. Untreated strep throat in rare cases can cause serious complications. These include rheumatic heart disease which generally is permanent damage. There is a window of a week or so where treatment with appropriate antibiotics will prevent this problem. You need to see your doctor for proper diagnosis.