Re: 9 months old and in 5th percentile for weight
I don't think there is any reason for you to be concerned.
First of all, the charts most doctors use are based on the weights of formula fed infants, so they are skewed toward heavier children. Breastfed babies have a much wider range of 'normal' than formula fed babies, and therefore should be guaged on a different chart. The WHO has a chart for breastfed babies that you can check yourself. Here is a link to the WHO infant weight-for-age chart for girls:
Second, your child is within the normal range even for formula fed babies. She is on the small end, but it is still normal. The only concern should be if she was a higher percentile previously and suddenly dropped to 5th %ile recently. Do you know what her %ile was at her last visit? Even if it has dropped, it is common for that to happen when a child starts being mobile- crawling or walking, so if something like that is going on, it could explain a sudden drop.
My daughter has been small since birth. Many of the women here have smaller babies and it's really nothing to worry about. She has stayed right around 5th %ile (which equated to about 15th %ile on the WHO charts) for weight and her pediatrician has never been concerned. Did your doctor express any other reasons for his/her concern?
Please don't feel like you've failed or aren't meeting your child's needs just because she is small. I'm sorry I don't have any advice for getting her to drink pediasure- I tried to give it to my daughter when she had a stomach virus and I never could get her to drink it. Maybe you could just try to encourage her to breastfeed more frequently or for longer stretches of time.
“We are not put on earth for ourselves, but are placed here for each other. If you are there always for others, then in time of need, someone will be there for you.”