A: It stands for Obsessive Compulsive Disorder. It's a condition where one feels the urge to repeatedly do particular tasks, like washing hands or checking to make sure the stove is off, etc. It's loosely used (like the word "retarded") to mean, essentially, freaking out over small things.
A: My opinion: You'll be out of high school before you know it! By the time you're 25, the age difference is NOTHING! The true test of your relationship will be the college years. Give it a go!