"i had realy rough sex yesterday and now I notice two large white patches on both sides of my vaginal opening and whitish discharge. What could it be?

Wounds. Without a picture (please no!) or an examination, it is too difficult to let you know what it could be. The general types of things in the differential would be friction pressure sores or an infectious process. I can only suggest that you refrain from intercourse and seek an appointment with a clinician for a more complete history and examination.
Possible yeast. It is impossible to know what the discharge might be without an examination and test. Usually they can test for that in the office and under a microscope. Thick white discharge oftentimes turns out to be yeast and can be treated. If this doesn't resolve then see your physician.