2000 Nissan Sentra Engine turns but won´t start

This morning, after I came back home from an errand, the car was running fine on the way over, but on the way back, thera were some kind of pulls (or jolts) coming from the engine, kind of like a sudden loss of power, I was able to make it home but that was it, the car wouldn´t start again, I then replaced the distributor cap, the rotor, cleaned the sparkplugs, and still nothing, no power. The engine turns but it will not start. PLEASE, please help me solve this problem, since my wife and I depend on this car A LOT!!!