This is not a typical STD symptom. Did you have any sexual encounter that could suggest you got those cankers because of that ? If not, you should visit your dentist/hygienist to check your mouth.
Is this a canker sore in your mouth? Those are not related to STDs. If you mean sores on your mouth, like a cold sore, that could be hsv1.
Lots of things cause canker sores (the ones IN your mouth), and your dentist or doctor can help determine the cause of yours.
If you received unprotected oral sex, you wouldn't get symptoms in your mouth. If you gave unprotected oral sex, it's possible, but not at all likely, that you'd get oral hsv2. This is RARE, and doesn't usually recur like yours is.
In any case, it sounds like a doctor or dentist needs to see what's happening so they can diagnose.