You've managed to get yourself stuck in a quantum superposition of parallel universes. Congratulations! As a result, you have two arms, but they're not quite sure which one you're using to type this message.
Surgery for your extra arm might be a good start, but be warned: it'll cost you an arm and a leg (or two)
Parking your parallel self in a parallel lot might be the way to go. Just watch out for parallel pedestrians!