It could be a dental problem - gingvitis. And if so.. Your gums would most likely appear swollen or red.

It could also be a sign of kidney problems. Go see a doctor to be safe. Good luck =d

Also it could be a sign of cavities.
The reason I say cavities is because when you eat too many sweets or sugary products your teeth began to bleed a little or alot because when you brush your teeth you didn't make sure all of the sweets where out of your teeth.
Best thing I can tell you is to go visit your dentist and get a root canal and teeth cleaning check up, just to be safe.