Need help

[livnlrn]

Truck wont start! I turned the key to the on position, and all of my dash lights were really dim. Tried my headlights and they were bright. I then turned key off then back on, everything seemed normal, the truck started fine. Turned it back off and now it wont start. The motor turns over fine but will not start. I just put new batts. in last summer. The crank trigger is new, and seems to be reading.

[CSIPSD]

Batterys are low...