If you have a chronic sore throat, it may be a symptom of something more. You should get your adenoids and tonsils checked, to start. It could also be a stubborn or recurring sinus infection, since the drainage can cause a sore throat. You also might want to look into acid reflux. Sore throat is one of the most common symptoms, and will occur as often as reflux does. Bottom line, your sore throat may not be the problem, it may just be the symptom.
Whatever is causing it, know that you need to sterilize or replace your toothbrush too! Often, especially for strep, the germs hang out on your toothbrush and lead to infections coming back time and again. Sinus infections can lead to sore throats as the passageways are all connected. I suggest you see a doctor and ask them for a throat culture to determine the source of the infections. Good luck!
As others have stated, definitely visit your doctor to get your throat checked out. As for what you can do to stave off a recurring sore throat, try gargling warm salt water several times a day. It tastes gross, but it does help. If it doesn't help, then you probably have something more serious going on as mentioned previously. Good luck!