I was below and up forward when I suddenly became aware that the wind was picking up and we were changing course. As I started back to the cockpit to get to the controls and helm, I realized a squall had hit with intense winds. The boat heeled over to at least 45 degrees, instead of its usual 20 degrees. By this time, I was mid-ship in the galley, and struggling with the boat’s speed and angle. Getting to the cockpit, I saw the wind in the squall had hit 35 knots (38 mph), the rain was pelting down and the autopilot was beeping, indicating it had lost control. As I got to the helm to take over, the boat gybed - I was too late. The boat spun into a new course. The wind backed the main and the boom came crashing over. As it did so the strap that holds the sheets that control the main sail gave way. The detached block became a missile and struck me on my right, lower back with such a forced my knees buckled. The boom now swung wildly and with great force, slamming up against the shrouds - the rods that hold the mast in place.