If you are, or were, driving the car then the car would do some serious jerking. That's from the water that runs through the engine getting into the cylinder head.
Also, you can check your spark plugs to see if one of them is wet or has some rust on it. That comes from the water getting into the chamber with the spark plug.
What ever plug you find that is wet, that is where you have the blown head gasket. If it's on the back then your head gasket on the back is blown. If a plug is wet in the front then the front gasket is blown.
Good luck with that. I had a blown head gasket on my Lumina and it's no joke breaking down the engine to get to the gaskets.