My 3mths baby also refuse to drink his milk. He was on breast milk, then I gradually intro FM. Now on full FM as I am going back to work. He started to have this prob since a few weeks back. He went on for 14 hours without milk once.
We brought him to pediatrician, checked him to see if he has ear infection etc that could make drinking milk painful. He is clear of these probs. pediatrician say as long as he is gaining weight he is ok, his system is adjusting as his weight gain has been very rapid (but my son not overweight at all) and now slowing down. On the 2 days he went on milk strike (he drank only around 3 feeds of 7 oz each), he became less chubby.
My mother in law suggested changing FM brand. Out of desparation, we changed from Similac to Nan 1. dont't know if it is coincidence, he drank every drop of Nan. Then after 1 week plus (we were just thru half way of the 2nd small tin of Nan), he started to refuse his milk again. When he began his first signs of rejecting some feeds, we got another brand of milk ready, this time Mamex Gold. Yesterday, he refused to drink his Nan milk again, and we swapped immediately to Mamex, he finished the milk.
I dont't think it is a good idea to keep changing FM, but what is really wrong with baby ?