NAVSUP,
Go to the DFAS site and select MyPay (halfway down on the left) It will prompt you for your social, I believe, and a PIN. Since you won't have a pin, follow the link below that says "Need a new PIN?" I'm not sure if you'll get instant access, but once you do, it's extremely helpful. The Leave and Earnings Statement (LES), if you haven't seen one, should give you all the info you need to figure out why you got paid what you did. Remember, in the military, you get paid after you do the work. So, your 15 OCT pay is for 1-14 OCT. Your end of month (EOM on the LES) pay is for 15 OCT until the last day of the month, etc. I can say after a commission, two changes of station, and one promotion, they will get your pay right, but it may take some time. Be patient and don't give up until you get an answer that makes sense.
Penguin