Being pretty sure doesn't cut it - do a load test on the battery regardless of age, often batteries set on the shelf for years before being sold, especially non OEM types - maybe the battery cables need cleaning.
If it starts ok with jumper cables or a battery booster in place, then it's has to be related to the battery. Put a volt meter across the battery when the key is off and all lights off, including the under hood light and see if something is draining your battery when the truck is parked. Also check how many volts are being drawn when the starter is engaged. Maybe the starter is going bad and drawing too much current. Do you have any after market accessories that may be draining your battery, like a radio amplifier that stays on when the truck is parked?
You need to check these things out - only takes a minute to check them.