Baby weight gain problems

AndromedaEclipse

I took DD to the pediatrician for her 6 month check up on Friday.  Usually I feed her directly before the appointment, but I didn't this time because we were running late. 

She had only gained 6 oz in 2 months which put her from the 40th percentile to the 9th percentile.  The doctor was concerned, and told me to take fenugreek and blessed thistle (which I am now taking). 

We just started her on solid fruits and vegetables (no cereals) on Christmas, and I'm pushing her to nurse every two hours or so where she used to nurse somewhere between 2 and 4 hours.  She's a happy baby, she has little chubby wrists and little chubby legs.  Since she pulls herself all over our house, I figured she was just active.  I don't understand why she isn't gaining weight.  Any thoughts/recommendations/similar stories?