Question for all the mommys with 4 kids!

I currently have 3 kids. I have a 5 year old dauther, a 4 year old son, and a 2 year old dauther. I am currently 21 &4 days pregnant and im getting scared. Is it harder with 4 kids? My 2 oldest are some what behaved. But my youngest is a snob.(sorry, but couldnt think of another word.) I been potty training her this past 2 weeks and we still are struggling with it. I am due july 29th. I know once the baby comes, the motherly instincts kick in but i havnt delt with having a baby in almost 3 years and im scared. Any advise on potty training and having four kids would be much appreciated. Thank you!