Love hurts, so the old adage goes, but what about the act of love? While sex certainly causes its share of bumps, bruises and burning, there is a difference between the kind of pain that accompanies a wild night of going at it and a chronic pain you feel every time you do the deed. If you've been suffering between the sheets, read on for some clues as to what might be putting the kink into your sex life (or taking the kink out of it, depending on your tastes). In general, there are three basic reasons as to why moans of oohhhh become cries of ouch: Physical problems or emotional issues…