Gas leaking underneath van

My van just started to perform poorly. Every time I start it, the engine shakes, and it has no power at all. There is gas leaking out the exhaust pipe behind the cat converter, and there is white vapor coming out the tail pipe. I checked for air bubbles in the coolant overflow thinking it might be a blown head gasket, but no bubbles. Any ideas? This is my only car and I need help really soon. Thank you!