For the past few months, off and on, there have been some small, greenish looking sores on the inside of my cheeks and lips. They cant be any kind of std, since my fiance and myself have both been checked after they started appearing. They usually last a few days to a couple weeks, and then go away. I havent had one in a month or two, but now they are comming back. Anyone know what this could be?

Also, at my fiance's insestence, I gargled some salt and vinegar, since thats supposed to heal sores in the mouth. today is the second day I did this, and one of them seems to have gotten deeper. Just in case that helps.