If you do not have the FOB and you are using your key to unlock the drivers door, and that sets off the anti-theft; the switch on the key tumbler in the door has fallen off or is bad.
So, to get it running:
Get in, close the door.
Turn the ignition on (DO NOT ATTEMPT TO START YET)
Cycle the door locks 5-7 times.
Turn the key off.
Open the drivers door and get out.
lock the doors and close the drivers door.
Now use your key to enter on the PASSENGER side.
Reach across and unlock the doors using the drivers door switch.
Now you can get in a start the truck.
You will need to fix the door lock anti-theft switch in the door, or buy a FOB, to avoid having to enter through the passenger door.