Milk for Pregnant

Hello po. i'm 15weeks pregnant and I was advised by my OB to drink maternity milk na pero sabi kasi ng isang friend ko lahat ng kilala nya na nag anmum or maternity milk lahat nag gain ng weight or tumaba kaya di sya uminom nung nagbuntis sya. I told my OB na ayaw ko mag gain masyado kasi sobrang tangkad ko kaya i wanna keep my weight sana while pregnant dahil mahirap maglose after birth pero sabi nya meron naman daw Anmum Lite. Any recommendations po? or mga experience nyo? thank you so much