fighting his bottle


my son is 7 weeks this week and he is just fighting the last 2 ounces of his bottle lately. like it's a chore to get him to finish his bottle. does any one else's? he's gotten to where he wiggles and wiggles and knocks the bottle out of his mouth. when hes sleepy he holds a mouthful in and then just spits it out wasting milk. its getting frustrating. we've been on the same formula for weeks now. 3rd can.