Something is not right here. The symptoms you are describing just don't add up.
One of two things is happening (or not happening). Either
1. your clutch is not engaging with the flywheel on the back of the engine to transmit the torque to the transmission input shaft
2. the transmission is not really going into gear when you think it's in gear
The default position for the clutch disk is against the flywheel. It's constructed in such a way with the pressure plate so that it needs a reason to move off the flywheel. This is the purpose of the clutch pedal, master cylinder, and slave cylinder. The slave cylinder acts on a lever that lifts the clutch disk away from the flywheel. It possible to get clutch slippage as the clutch disk wears or if the crankshaft oil seal starts to leak, but it would be a gradual thing and not likely to act so quickly that you could've driven it last night and not today.
I find it much more plausible that something is wrong internally with the gearbox, like a selector fork, but it seems really odd that none of the gears would work.