So I'm 18. Both me and my boyfriend still live with our parents but he has a huge bedroom upstairs…

So I'm 18. Both me and my boyfriend still live with our parents but he has a huge bedroom upstairs where we get privacy whereas at my house I share a room with my sister. Obviously after the baby is born I'll come to my parents because I really don't think climbing up and down stairs with stitches is a good idea but after healing and getting into the groove of motherhood I plan to move in with my boyfriend...I just don't know how to tell my parents :/

I know my boyfriend won't want to move in at my parents house and that makes sense because 3 people and a baby in one room is going to be so crowded and we'll have absolutely no independence to do it on our own but how do I explain that to my parents without them getting hurt?