A lot actually.
First of all, when the battery starts going dead all the time, its whats called a "sign". Sorta like when you feel a pain and see arterial blood squirting out.....
Unfortunately, you ignored the "sign" so now you have even more to fix.
Start with the basics. Pull off the battery terminal clamps and clean them.
Make sure that the wires on the starter are tight. The truck gets its power from one of them.
There is a fusible link in the wiring harness. This is a piece of wire that is smaller than the rest of the wire in the circuit and has special nonflammable insulation.
In case of an overload, it melts and opens the circuit to prevent a fire.
What has probably happened, is that the alternator has been trying to charge a failing battery and it finally got to the point that the fusible link from the rest of the truck to the terminal on the starter got overloaded by the amount of current that the alternator was trying to pump into a shorted battery and it melted and killed all the power to the truck.
If it did not blow the fusible link from the alternator, then it might have kept the truck running with the battery out of the circuit until you switched it off.
Not sure, I would have to look at the schematic again.
Either way, you are going to have to check the fusible link from the starter solenoid to the rest of the truck.
It will be hooked to the same terminal that the big battery cable is hooked to on the solenoid.
No sure where the link is, but it will be a dark brown wire spliced to a red wire if its original
It MUST be replaced with either a fuse or the same size wire.
If you use bigger wire, your next post will probably have the words "fire" or "burnt up" in it.
See if you can find that link. It might be obviously burned or not. But, if not, you can usually tell by pulling on each end.
Good wire will just stay there, melted wire will let the insulation stretch.
If you don't see anything obvious, grab a voltmeter and post back.
We can talk you through finding the broken circuit.
