I have a thick white discharge from my vagina and it itches. Could I have a yeast infection?

Yes. It sounds like you are describing a yeast infection. Try over the counter Miconazole preparations. If you are still having symptoms, be sure to see your gynecologist.
Possibly. Most likely the answer is yes. If you have never had a yeast infection before, see a doctor first to make the correct diagnosis. Yeast infections are very common, especially in the summer months and after taking certain types of antibiotics and easily cured with over the counter medication. Rarely, it may also be a symptom of other health problems like uncontrolled diabetes or immune disorders.