Help with canker sores?

Help! I keep getting canker sores in my mouth,and they HURT. Right now I have one on the piece of skin that connects your mouth,and it is very painful.For most of the canker sores I get,I use mouthwash to make them stop hurting but this one still hurts even after I do the mouthwash.Please answer! I need the following answered: How to make them heal fast,remedies,and how I can prevent them.Thanks!