You told yourself it was only physical. You lied.
I never understood the term "friends with benefits." It implies there's no benefit to simply having a friend. "Lovers without obligation" seems more apt.
No matter what you call it, you can definitely file it under "it's complicated" in terms of Facebook relationship status, especially when you start to see more than just booty in your booty call.
Inevitably, this is how that rollercoaster of emotions will go down: