Car trouble. Could it be fuel filter?

Fuel filters don't get plugged instantly. They take a long time to get clogged up. There's a lot of things that can cause a car to slow down. There could be an engine running problem, a transmission problem, or dragging brakes. Based on your description, my guess is the transmission went into default mode. You didn't say what happened after that, but typically you just need to turn the ignition switch off, then restart the engine to get it back to normal operation.