Hi Tracey,
I went through this with my 4th child and here is what I did and it didn't take her long to get her back on track. So every baby has a regular eating/feeding internal clock for instance my oldest every 2 hours/4 oz (that sucked), my 2nd was every 4 hours6oz and my 3rd was every 3 hours/8oz and my 4th was every 4 hours/8ozs.
Ok here is what to do.. feed on either every 3 hours or every 4 hours which ever you prefer. Don't feed him any later or earlier, so if you are going with every 3 than he would eat at 6am, 9am, 12pm(noon), 3pm, 6pm, 9pm, 12pm(midnight) and then again at 3am. Or you could go every 4 which would be 6am, 10am, 2pm, 6pm, 10pm, 2am, 6am, this is the one my daughter has been on since she was born. I would go with 4 ounces or so and then work up from there, as he grows he will become acustomed to this schedule. In the daytime keep the shades open and lights on in his room or living room. Put him in things that he would be in when he is awake like laying under a toy, in a bouncy seat or anything else. And then as it starts getting later in the evening you start shutting off the lights, turning down the t.v, etc. In the middle of the night feedings only turn on 1 light and adjacent from where you are. Like if you feed him in his room than turn on the bathroom light or a hall light. Do the same routine no matter what, change his diaper than feed him. When you get up in the morning change his diaper and get him dressed for the day. This will also help. At 9pm everynight you would want to give him his bath and get him ready for bed (this is bath, bottle, book and then bed that you could start now). I formula fed all my babies so if you are breastfeeding than you would probably move the feeding times closer together like 2 or 3 hours or so. I hope this helps you, if you have any questions feel free to send me a message. W.
P.S. follow this routine and stay on it and you will have him back on track in a few days I promise.