Re: Do I have a problem?
with the PP. As long as you're feeding on demand, my guess is that the decline in percentiles is the normal "leaning out" that tends to take place as breastfed babies go from being essentially sedentary to expending more and more calories on motion. At this point your baby is probably doing more kicking/rolling/reaching, and that can use up a lot of calories that previously got packed on as fat. Both my girls dropped significantly in their weight-for-age percentiles between 2 and 4 months, and dropped more between 4 and 6 months. Their pediatrician didn't care because she's familiar with the growth patterns of breastfed babies.
That being said, yes, please get your thyroid checked!!! It's really common for a moms to experience something called postpartum thryoiditis, and a typical progression would be for a mom to go through a hyperthyroid phase, followed by a hypothyroid phase. Postpartum thyroiditis is more common in women with preexisting thyroid conditions, so you definitely want to stay on top of this and get tested frequently.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"