Hi Victoria: You are lucky you are recogoning this problem now. Your baby may have Acid Reflux. I have a 6 mo old who spit up my breat milk (as well as any formula) and still spits up at this age. These are all the tips I've learned over the past few months:
First off, instead of feeding him lying down on a boppy pillow (or anything else) try to sit him up as much as possible while nursing. It's hard to digest if he's lying down or parrallel. Next, only feed him for a few minutes, then try to burp him. I know this is hard b/c he will probably start crying but you have to get him to burp before giving him more. As, you probalby know, there are a few different ways to try and burp him. If you do ever give him a bottle, keep him down to a minimal amount and then burp him. Sometimes massaging his belly after he's done eating will help it digest.
And last but very important, do not lie him down to sleep, even if he falls asleep while he's nursing. He will eventully burp while he's sleeping and spit up. Even if you have to hold him while he's sleeping, try holding him in an upright position so the food can digest, or try putting him to sleep in a swing that is upright. Do not lie him down and play with him, giggle him, anything for at least 30-45 minutes after he eats. This is probably hard as well, b/c he might want to eat again in an hour or so, but it might help.
If you keep having problems, talk to your doctor and they might suggest Zantac or a different formula if you supplement.