bloody discharge???

A week ago i had protected sex and today i had a bloody discharge. The intercourse happened a day after my period ended so i wasn't ovulating and it is supposed to come in 2 weeks. I've been feeling bloated and my back's been hurting for the last couple days. I have to mention that i don't usually wear socks while i'm at home and lately the temperature outside has been below 0 degrees celsius (32 fahrenheit) for the past week. Any idea what it could be?