I bought a brand new starter, alternator, and battery new batteries keep dying out

Check for parasitic draw http://www.wikihow.com/Find-a-Parasitic-Battery-Drain explains it very well the only thing it doesn't say is what the acceptable level is anything under 0.05 mA shouldnt cause this. there is typically always going to be some sort of minor draw due to the ECM retaining information such as drive cycles etc and radios retaining your presets and time also i would check your ground connections between the battery and the body and the battery and the block.

You have a drain on the battery somewhere. It could be as simple as your glove box light staying on when the door is closed.

The easiest way to find the problem is to set a meter in line to monitor amperage draw, then pull individual fuses until you find the circuit responsible for the power draw. After you identify the circuit, you can inspect it closer to see why it is pulling power.

If you don't believe you can chase down the power draw, any shop would be able to hunt down the problem for you, but sometimes electrical issues can be time-consuming to identify the problem.