What Causes Vitiligo?

I went to the doctor around a month a go as I had noticed two round white cirlces on my thigh. She took a skin sample and sent away and the results showed negative for any kind of fungal infection. Since then I had a sunbed, burnt badly and now my skin is peeling away and forming random white patches. I dont know if this is due to the sun burn or vitiligo. When you have vitiligo does the skin peel? We have no history of vitiligo in my family. I'm a 27 year old white british female who has a good health history.