Baby hardly drink his formula milk.

Does every mother experiencing the same problem with me? Part of it maybe?
But, how do you handle it?
I had searched from the google, some says because the baby is teething, sick, bla bla bla.
My baby isn't sick, but teething... maybe lah.
I don't want my baby to lose his weight. So instead of just giving him 6oz per 4 hours and he won't even finish his 6 oz, I decided to decreased his formula milk from 6oz to 4 oz, sometimes 5oz. Give him little but many time.
It helps tho. If you, mothers out there have any idea, feel free to tell me.:)