Foods/Methods to put more weight on my 13 month old?

My 13m old(14m on 29th)is weighing in@20lbs 1ozs-20lbs 3ozs on my home baby scale and was weighing 20lbs also at the Ped's office scale. My Pediatrician wasn't concerned by her weight being on the lower end, but I know she's underweight from what I've read and the fact she still wears size 12m clothes when she should be entering 18m clothes by now. I feel like a bad mother because she should weigh more, but she doesn't want to eat much right now that she's getting all 4 of her canine teeth in and she is mostly sucking down milk and picks at her food I feed her. She also is chewing on her fingers, toys and pacifiers. I don't want to call my Ped's office for an appt just yet and sound like a crazy mom all worried about her weight gain and have them laugh at me. I want to see if you all have some advice and try it before I make an appt over this. I've never had this problem with my other child, but I was underweight as a child(not as baby/toddler that I know of)if that matters.