Anyone have a mommas boy/girl and expecting...

So I have a 3 yr old boy and his is super attached to me and I am so worried about the transmission of me having a new baby and it sleeping in my room BC I tell him no that he has to be a big boy and sleep in his room and the baby getting a bunch of new stuff also he will be starting preschool only a month or two after baby arrives. Anyone have advice I just don't want him to feel left out or unloved :(