There will always be power to some fuses, while others only get power when the key is on. So detecting power at some locations is not automatically indicative of a problem.
If you're detecting current flow however, then yes, that's an issue. Take the offending fuses out until you detect no drain and you've at least found the circuit(s), if not the actual issue.
Other items that often cause a drain are the voltage regulator and alternator. If you pull the 3-wire plug off the regulator and the power drain goes away, there you go.
If you pull the main charge wire off the back of the alternator and the drain goes away, bingo.
Viperwolf will know what causes the problems, and probably other possible causes as well, but you will need to keep digging.
And frankly, a drained battery in a month is not that much drain. Lots of vehicles won't take sitting that long without losing the ability to start. Radios, computers and other accessories can draw just a tiny bit, but added up over a month, and you've got a weak/dead battery.
And a bad battery itself can do the same thing. Different batteries discharge at different rates I think. And an older weaker one might discharge quicker still.
Maybe the others can confirm all that, but I guess the way to test the battery itself would be to isconnect if from the truck and see if it still drains.
Good luck.
Paul
