My baby's situation is just same as yours. At first, it is just some red 油滋粒. As advice by the nurse, she said it is 皮膚敏感 and ask me to clean it with water more often. But one week later, there is no improvement and some yellow liquid flow out. We consult the doctor at once, he said it is 濕疹. That means we should not clean it so often. My baby's situation is very serious. The whole face is becoming red and it seems to spreading to the neck and body.
So I strongly advice u to consult the doctor immediately.
by the way, My baby is also BF and the doctor said it doen't matter and the reasons is not yet confirmed