I've been seeing the same person for two years. I love her very much and she's all that I could ask with one exception: sex isn't as fun as it used to be. This is my first relationship that has lasted this long and recently, I've noticed I'm flirting with girls from my past (flings and exs). While it's just over IM and I have no intention of ever cheating on my girlfriend, is this normal? After two years, is it pretty standard to "get bored?"