Every baby has their own schedule, this is true, but it can't hurt to try some techniques to encourage him to sleep more. I'm sure you're not doing anything "wrong" --some babies just need that extra feeding.
Here's what has worked for me-- my 10 week second daughter is breastfed and sleeps in her crib 10-6. If some of these techniques work for you, great, if not, don't worry about it! Your son will eventually sleep through the night. I just know sleep is important and it sounds like you want some help. :-)
1. Space feedings closer together in the late afternoon, early evening. Rather than eating "big portions" every 3-4 hours, try having smaller portions every 1-2 hours later in the day. To get dinner cooked, take turns feeding the baby.
2. Have his most awake time be in the late afternoon, early evening. My daughter take a shorter nap in the late afternoon (5-6pm) and then she's up until we start the bedtime routine at 7pm.
3. Follow a consistent bedtime routine: bath, lotion/massage, pj's, final feeding, rocked/held to sleep and put down.
4. This sounds cazy, but its been known to work. Try putting your son to bed earlier. Instead of 9-10 pm, try 8-9pm or 7-8 pm.
5. During the night, make sure he's really awake when you go in to feed him. Just wait 5 mins when you hear him stir and see if he'll fall back to sleep on his own. Obviously, if he is freaking out crying, go in right away, but if its a couple of short wails, he might not be truly awake. Babies go through cycles during their sleep where they will briefly wake up or be close to waking up before returning back to deep sleep.
Like I said, this worked for me and I just want to pass the info along. I don't want to impose my routine on you, just want to help another mom get some sleep. So, pick and choose or adapt what works for you.
Good luck & Sweet dreams!
HTH
-Kate