Hi M.-
At your son's age, he needs to drink at least 32oz of breastmilk or formula a day (thats 5-6 6OZ bottles in a 24 hour period) - but rest assured that you are NOT feeding him too much! Count yourself very lucky - so many parents of infants and toddlers have picky eaters, and have to be constantly worried and on top of how much their baby is eating. Your baby is not one of those children, and neither was my daughter! My little one had doubled her birth weight by 3 months, and I have never had to worry for one second if she was getting enough nutrition - she is now 1 1/2, eats three adult sized meals a day with 2-3 snacks in between, and is the healthiest, least picky child I have ever met. Its so nice to not have to worry about how much food she is getting.
Also rest assured that your son WILL stop eating when he is filled - babies do not know how to "overeat" - they merely eat until their stomachs feel full. Because he is not taking his bottle during the day, try putting his milk or formula in a sippy cup and see if he will drink it that way during meal time (babies his age generally take to the sippy cup really well as long as you get the Avent cups with the soft, sippy nipple on it. You can get them at the grocery store). If he is still not wanting to take his bottles, I'd cut down to one container of food at meal time and offer him the bottle before or after he eats his solids. My daughter started rejecting her bottle for food at about his age, but my pediatirician really stressed the fact that she needed to drink at least 32 oz. in a 24 hour period for proper body and brain developement. If you can see if you can stick a bottle in in between meals so you are feeding him food/bottle/food/bottle throughout the day.
Count yourself very lucky that you have a good, happy eater on your hands :)
Good luck!