Early pregnancy symptoms

I had unprotected sex on Saturday the 7th and started feeling vey crampy, have excess milky discharge, lower back pain and brief moments of nausea on Monday the 10th. I looked up my ovulation cycle and it said it should be between the 3rd and the 9th. I am not due for my period for another 11 days. Has anyone else ever experienced symptoms this early and been pregnant? Or does anyone know what else it could be?