Chris DHang in there Louise. That first year can be really tough, but it will get easier. It seems to be really common for the little ones to pack on the weight before their systems adjust to the meds.
My son was almost 22 pounds by 4 months. He was just huge. He was my firstborn and I wanted everything to be perfect for him. I was so sad about it all.
It did get better though - and we learned to adjust. His weight evened out quite a bit. He weighed 24 pounds on his first birthday.
(In all honesty, we do currently have a problem with weight now, but that is probably due to many factors - and quite a long story - maybe best saved for another post)
I feel for you! I know too well about leaving the doctor’s office feeling just sick. You are doing what you can; some things are out of your control. The people who post here will help you learn so much.
-Chris