It's likely the alternator itself that's taken the 'biscuit'.
If you want a second opinion, especially if you aren't familiar with this type of diagnosis, I'd strongly recommend taking the truck to autozone or any other auto parts store. They'll check your battery and alternator for free in most cases right there in the parking lot.
One thing I'd like to share, 12.6 volts is usually regarded as the 'magic number' with batteries. To build upon RonD's posts, I'm going to post two or three videos about alternators, batteries, etc by Ericthecarguy. There's some useful information to take away from these videos for not only alternators and charging but for general electrical mishaps, general know-how, and other things along those lines.
I'm not trying to scare you here with this next line or two, but there is something you need to be aware of if you aren't already. Lead acid batteries can explode. I do mean explode, btw. While leadacid batteries themselves are very good at coping with misuse or overcharging, overdischarging type situations, it's important to know that it is still none the less possible. Definitely wear safety glasses!
As a couple general rules and tips, follow these at all times and you'll be fine; usually.
1. Never stand directly over a battery for any reason while it is hooked up to either a vehicle or a charger, or while it is being jump-started using any method.
2. If you smell rotten eggs (usually only takes place with older batteries) stop what you're doing immediately
and cut the engine if it is running at the time and get the battery to open air, IE, outside. best way to avoid this is to do any work around it while you're outside in the first place. This gas is very flammable and, again, can explode if ignited.
3. Avoid sparks or flame of any kind near the battery. Propane torches, cigarettes, etc.
4. If you solder battery terminals on, do remove the battery first and wait until the terminals have cooled until they can be touched bare handed before reinstalling.
5. If you need to remove the battery, remove the negative cable first then positive. Connect positive first and negative last when installing.
6. Never set tools (like wrenches or screwdrivers) on top of a battery. These can cross the terminals and you end up with a very dangerous situation.
Again, not wanting to scare you, but I feel it's worth mentioning. I'd sure want someone to tell me if this were possible.