Why does the skin at my fingernail's cuticle tear back?

This has happened for awhile now, probably since I started high school,or maybe earlier and I'm 18 and graduated now.. My skin has always peeled back from the bottoms of my fingernails (the cuticle or "eponychium"(sp?))..my science teacher once said it's from exposure to bacteria, or not washing my hands enough.. But I'm a freak about my hands feeling sticky and touching the keyboard,xbox 360 controller, etc. so I know I wash my hands more than normal people.. anyone know why these little pieces of skin are randomly ripped up abd red and sore?? Looking at my bottom cuticles,just about all my fingers are shiny at the bottom edge from this happening to them all at one point..please reply..thank you =)