I dont know if thats a wisdom tooth or an infection its at the back of my mouth and my gum is swollen and a bit white but no signs of a tooth?

This symptom is called PERICORONITIS, which is common around unerupted lower third molars. You can rinse with warm water and salt rinses, take pain relievers, but best see a dentist for treatment and removal of the swollen tissue so tooth can erupt. If tooth impacted, than it should be removed. Get an x-ray to see the disposition of the wisdom tooth.

It may be a wisdom tooth trying to erupt .Normal but uncomfortable. But it may be one of scores of other intra-oral problems. You need to be examined and x-rayed to be diagnosed. Only with accurate diagnoses can the appropriate treatment be recommended. Considering your age and description, I would recommend that you see a wisdom tooth expert, a specialist Oral Surgeon.