It has passed for me but I felt similar feelings at times about my dd after my son was born. And they are both my biological children.
I think it is a hormonal thing to make us care for the one that needs is the most. Newborns are...
When I night weaned mine at 18 months and the other 2.5 they immediately started sleeping better. I think having to digest all night long was waking them, then they ate again and again and again. They took like two nights and were done.
A dentist called Dr Ellie said she has seen baking soda use for cleaning teeth strongly correlated to receding gums, so she doesn't recommend using it. You can find her site and read more.