its probably a growth spurt. im still breastfeeding my 19 month old son, and sometimes during that first year, i think sometimes i was nursing him every 15 minutes!
i want to say on a side note that breastmilk is made on supply and demand, the more baby nurses, the more you make... so you dont have to suppliment with any formula, but for lots of moms it is easier.
telling you how many ounces he should have is hard because it depends on the child, their size, whether they are in a growth spurt... etc.. the list goes on. just nurse/feed him until he stops eating. you shouldnt worry about the exact amount unless he has trouble gaining weight (which usually isnt a problem either really.... sometimes they stop gaining weight while they arent in a growth spurt..)
dont stress about it. he will eat when hes hungry, as long as you or someone feeds him at that time, he shouldnt have a problem determining when hes hungry and full.
the problem with appointing an ounce amount is that moms will then sometimes feel obligated to make sure baby has that amount and they will sometimes overfeed baby... causing that little signal that tells baby he or she is full to stop working. you want that to be working, so just feed until baby stops eating, and he will tell you when hes hungry again.
during the first year baby will double his length and triple his weight - so thats a LOT of growing.... it will literally feel, or actually be, every 15 minutes between eating during some days LOL. so just have patience, and dont worry so much about a specific amount as you should worry about making sure you are just responding to your son and feeding him when hes hungry, and dont pressure him to finish a bottle or anything.
i really want to support your breastfeeding efforts. if you feel like you are having some trouble, look for the local le leche league in your area... they will be able to help you a LOT with all the different aspects of feeding. i dont want to make you feel bad about supplimenting, but unless there is weight gain problems, or other health issues, you shuold have enough milk, as long as you have the demand, you will have a supply. but, like i said, some moms find it easier to have a bit of formula involved.
if you are interested in my story, my son was totally breastfed, and even though i tried pumping and bottles, my son didnt have any interest in it. i now have a few bags frozen in the freezer, and they work GREAT for healing cuts, scrapes, etc.. literally it took 2 days for a skinned knee to heal, no scab involved! it was fantastic!
anyway, i have had a wonderful experience and i would like to support other moms who wish to continue breastfeeding ... so just send me a note if you want!
anyway, www.askdrsears.com has great info.
www.llli.org is le leche league