RealGM

for half a year my car has had problems starting. the lights, windows, a/c radio, etc, work fine, but the car engine doesnt turn on. could it be the battery or the starter or something else? the battery tested recently and it came out as a bad battery, not surprised. usually a jumpstart gets the car running but last week that didnt work, even a towman's truck couldnt start it.

the car has started since then but i only drove it twice, and it started really slow. usually when that happens all i need is to charge the battery but that didnt work. so it has to be the battery right? btw i always clean the corrosion on the battery and clamps.

change the battery in mid air while parachuting like those Advance Auto Parts commercials.

alternator?

what kind of car is it?

My car did some of those things before. The engine would not fully turnover and my engine would cut of or sometimes my car would die while driving it. What I did was turn up my car and cleaned my carbonator. When your car is started does your rpm move up and down while your car is stationary or rather you hear you engine revving up while stationary? Because that is what my did.

how old is your car? and what type?
when i was teen driving my dad chevy i see this problem few time
since then we decided to buy toyota and i'm still driving toyota (not the same car)

i have the privilege of driving the beautiful 1998 nissan sentra , since we cant tell if its the battery, alternator or starter we decided to take it to a repair shop tomarrow, they better not take a long time. paid by the hour

No! the repair shop is so not worth it for this problem...
If the battery has been tested bad already, than that's probably the problem. you can't keep recharging a battery, it will stop holding charge. When you try to start the car, does it crank really slow or not at all, as in no sound? then its battery. If there's just a click then it's probably the starter if the battery has juice.
Alternator can be tested for free at kragen.
Can also be an ignition module or your sparks, but the car would be running horribly if that's the case.
it can also be an electrical connection that is involved in starting the car, so you have to find an wiring diagram and follow the wires on your car. could be a bad ground or loose connection. But thats probably last resort, it's most likely the battery since it's known to be bad and you keep jumping it all the time.