My 4 week old has always spit up alot since birth. She has also been very gassy since day one. DD has only breastfed...however I plan on introducing bottles this week as I plan on returning to work PT in 2 weeks. Recently (over the past few days to a week) her spit up has been thicker like mucous. She actually chokes on it occasionally. Is this normal ? She has also had a few looser BM. I just want to make sure that she's not sick. Also will this worsen as I introduce bottles ?