Fistofgod

Well to start off the problem im having is when i push the gas and release the clutch.... like if i let go of the clutch all the way and stomp the gas the car jerks like it doesnt wanna go.. i cannot spin tires also the car seems to just turn off... this happens through 1st and 2nd gear... somtimes 3rd... but when im in like 4th going about 40mph and i give it gas to take off the rpm just goes up, then i start going like its delaying.. I gotten New timing belt, disributor cap,rotor, spark plus wires, fuel filter, fuel pump,.. but when i put it in reverse i punch it it does fine! i fly going backwards it makes no sense really. im guessing the clutch could be slipping? but im not sure any. idea on this?