Why is my engine jittery?

-I have a 1999 Ford Ranger with 55,000 miles. I bought it used a few months ago and there is a problem that is getting progressively worse. If i am driving and i step on the gas to make it pick up speed, it kind of falters. It'll go but every 5 seconds or so itll jitter and jerk and then speed up and then jitter again. It feels like Maybe the clutch is making a bad connection and needs to be replaced, but im not sure. The clutch engages really far down in the pedal, Probably 1/2 to 3/4 of the way down until it engages, but I dont really have many problems with slipping the clutch. What might be the problem?LOW, low miles for a '99, could be rust in tank and fuel system- worst case. Could just need a minor tune-up: FUEL filter, air, plugs and wires. Sounds like a fuel delivery issue more so than a spark issue. All of which you can repair (tune-up wise). When you pull the fuel filter have a glass jar and blow through the filter and see what comes out. YES put your lips around the end of the dirty, gas filled filter (wipe off without loosing too much of whats inside), it want harm you! DON'T suck.