My car is losing power.... PLEASE HELP?

Its a 98 honda civic ex coupe. Everytime it goes over 4-5 rpm, it lag, and then accellerate again. Just today, when i let the car idle, it act like it wanted to die out. Someone said it was the fuel filter and the spark plug, so i change it, and still the problem remain. I even bought a new battery. Someone now said that its the distributor cap or the alternator that is causing the problem. I dont want to take anymore chance cause i'm on a budget, so can someone please help....