Start looking for a place of your own. For you, your boyfriend and the baby. This will definitely take away a lot of the stress and anxiety. If you start looking now you should be able to find a place for after baby is born. That's just way too many people to be living in one house.
I would kick them out or find a new place if you got the funds. Otherwise you might need to talk to them about how they are going to deal with a newborn. Maybe scare them into leaving. Lol
As far as keeping your cool, delegate special time for yourself. Bubble Bath time. Exercise or sex releases endorphines in your body that promotes healty happiness. Or talk to your boyfriend and let him know the visitors HAVE to go. Give them a deadline and let him know they have to leave and its for the sake of your family. How are you supposed to have time with your baby and our man with all those people? Its going to be hard enough for you two to change your relationship with a baby, you two do not need an audience for that. Explain that to them.