So I don't have the best teeth I have already had a root canal on my bottom last tooth but then on I have been doing my best by brushing my teeth better than before but today I realized that I had a hole on my bottom right canine or "vampire' tooth its hurts to drink cold things and you can see the gum here is a picture of it I toook with my phone please tell me if it's a cavity and can be filled (hopefully) or if I need another root canal...
http://tinypic.com/r/iypm48/6

without x-ray and proper inspection no one here knows for sure, so you go see the dentist, since either way they had to fix it

No one can make that decision without an exam.

Until you see the dentist get some Anbesol to numb the pain and use dental wax to temporarily fill the hole. You can put the Anbesol on some cotton and the put dental wax on top of it.

Generally the method doesn't work while eating.

I've looked at your photo and yes, it IS a cavity. The sooner you get it fixed the less chance you will have of needing a root canal.

When I looked at the photo I see you have white chalky areas along the gum line. These areas are ALL early cavities. You really need to be sure you are brushing well along the gum line and use a toothpaste like "MI paste" that will help to remineralize (strengthen) those weak spots.

Get to a dentist ASAP!