I have a 4 month old also! She turned four months yesterday and has her "well baby" appt. tomorrow. Mine is also a big one!
I had PID (Preganancy Induced Diabetes).
Ended up having to check my blood sugar 6x's a day and injecting sulin 3 x's a day into my stomach! It was terrible, espeically since I have such a "Needle phobia" (That's what the Doctor called it when I starting bawling, after being told I would have to do this). But I am fine now and so is baby.
Funy thing is, she's my 3rd, but the first regarding the diabetes.
She weighed 9.7 lbs and was 22" long! I'll check in after her appt. on Wednesday and tell ya how big she is now.