Would you please state her age so I am able to properly answer your question. Thank you.
My daughter was 17lbs and 29 inches at 2yrs and all I was told was as long as she is developing fine then don`t worry. I agree that you may have to encourage finger foods and regular meals. I am glad you are getting good advice here. I felt like no one listened to my concerns.
Her weight is very below the 5th percentile and height is just above the 10th percentile for her age. With Celiac Disease there may not be any outward symptoms. If she is absorbing issues then she would not be gaining weight. At 20 months old she should be eating finger foods 3 times a day with snacks between meals. You can still nurse her; however, it should not be her main source of food now. Suggest having her eat meals with you and give her breast milk in a sippy cup so that you can start to wean her off but she still has the breast milk for a while. Until you get a definite answer about Celiac Disease, suggest not giving her any wheat products. Best of luck to you.