2003 silverado something is messed

Ok I have a 2003 Chevy 1500 Z71 Off-road (it has the steering wheel controls.) And I was driving and the air bag light came on and I thought nothin of it then a code in the cluster comes up that says "battery not charging". I turn it off and turn it back on and my batt gauge is all the way down and now its says service 4wd and service brake booster and it says my door is open which it is not and my abs and parking break light come on and I know all of this stuff wouldnt go wrong all at once so is something messed in my computer or? its very frustrating and confusing because sometimes I will be in park and reverse lights are on or the dome light wont shut off inside the cab while driving or the mirrors dim and its dark out. Thanks in advance for any help

---------- Post added at 11:12 PM ---------- Previous post was at 11:10 PM ----------

oh and my radio does not turn on. alternator and battery are both good too