Getting rid of a neck

I've had success breastfeeding all of my babies, but only until they were about 6 months old. Then the milk dries up and I have to switch to formula. Which is fine with me, I'm not a huge fan of breastfeeding anyway--obviously it's the best thing for babies, but it gets really annoying. So I was getting pretty nervous when Allie got close to 6 months old because she would not take a bottle. In October we left her with my mom while we went to dinner and a movie and Allie totally refused to have anything to do with that bottle. In fact, she got really mad every time my mom tried to give it to her. But for a the past few weeks I've been really worried, especially since it was obvious she was not satisfied after each feeding. Then I was pretty sure she was not gaining as much weight as she should be. I kept trying to give her a bottle, she kept refusing. So I took her to the doctor, and unfortunately all my fears were confirmed. Here's what her growth chart looks like.
In the past 2 months her weigh gain has dropped dramatically.

He said she looks healthy, though, she doesn't look sick, but when he looks at her he notices she has a neck. Most babies don't have necks, just rolls of fat and double chins. He wrote "Failure to Thrive" on her file. Isn't it aweful?? He said, "I know it sounds terrible, all it means is she doesn't weigh as much as we want her to."

Plan A was to get her to east solids. So I went home and desperately tried to spoon feed her bananas, rice cereal, green beans, anything. She mostly just spits it out, though. And I was determined that I wasn't going to spoon feed her, I want to do Baby-led Weaning like my sister did with her baby. But that's a different blog post. I was so worried about her. So we decided to tackle the bottle issue. It only took one hour of crying, then she downed it! She was such a sad baby! Even after she drank it, for the rest of the day she was still a little heartbroken. But now she is eating like a champion. I think she's trying to make up for lost time, because she just keeps eating and eating. And her diapers! They are so soggy--she soaks through them in no time, she poops all day long, and she has a raging diaper rash. And I am so happy my baby is no longer wasting away.

We will get rid of that neck yet!