Cheers guys.
I looked it up earlier, too. I didn't know if it was something like, my teeth rubbing against the insides of my mouth that could cause them or whatnot.
Apparently hormones can create them - and I've had dodgy hormones this year, so that could be a reason.
I might try vitamins - I sure don't get enough - I'd rather find the reason and prevent them rather than battle them every time I get one. x__x