Discovery Home & Health

i have a 15 week old boy who has always been a great feeder but recently he has started only having 4 ounces in the morning and then at every other feed id taking approx 2 ounces and then screaming and screaming. I have recently changed the teats on his bottles to a faster flow and i'm not sure if he is swallowing a bit too much air, so i'm going to try the slower ones again, i also didn't know whether this was a sign that he needs weaning but he seems to be eating less than he did before, not more. Has anyone else had any problems in this area? if so please reply