These Canker SORES R KILLING ME!!!!!!?

those white circles in your mouth and hurts like hell the canker sores.I get them like all the time the longest i can go without em is like 1 week and half and ill get another. My canker sores get too be the size of half your pinky nail and they hurt alot. Is there something wrong with me and wut is the fastest way to get rid of them. I went to a doctor and he sed salt only helps it hurt less but does not make it heal faster. Help me PLZ!