Ring ring ring! We have a winner!
Now I understand why the doctor (didn't blow me off and) said soy protein sensitivity when I said I thought Cale slept better when I didn't eat soy: because even sleeping problems can be caused by protein sensitivity. Since I also think eggs are in this boat (probably egg white protein, thanks Daniel!) of causing baby sleep problems as well, that leaves me wondering just what protein is safe for me to eat, and soon safe for Cale to eat in baby food form.
One warning! When I was researching GERD, I learned that Similac Alimentum and Enfamil Nutraminagen are both milk-based. Both are broken down to be less likely to cause digestive upset for infants just sensitive to casein, but they are not strictly milk-free.