I think that I have a yeast infection but I'm not 100% sure so I don't know exactly how to treat it.?

Vaginitis. if you have itching and burning and sometimes ewelling of your private area, this is most likely fungal infection. When there is a cheesy secretion this is definitely a fungal infection that you may try to treat with over the counter vaginal applications of anti fungal creams ( usually there are applicators to insert intravaginally) . The duration of the treatment depends on the product.
Script/OTC. Diflucan (fluconazole) 150mg one time, or any OTC yeast prep will work No tub bath,sex,douching,tampoon till cured.