What is this growing pink spot/area on my hip?

Last week, I noticed a round pink area on my hip that looked exactly like what happens when you have pressure on your skin for too long (for example, leaning on your shoulder). I assumed it was just because I slept on my side overnight. However, the spot never faded and everyday it has gotten bigger even though I've stopped sleeping on that side. When I first noticed it, it was about 3 inches in diameter and very round, now it is about 12 inches in diameter and not round anymore (random amoeba-y shape now?). It is NOT itchy, sore, painful, or textured any differently normal skin. It still just looked like what happens when you apply pressure to your skin for too long and it turns pink, except now it's huge and not round anymore. I didn't experience any irritation in the area before it appeared or when it first appeared. It's been close to 10 days now since it first appeared and keeps getting bigger everyday. Does anyone have any idea of what this is?