Feeling more nervous... Third or more baby?

Karissa • Expecting #3 in September
DH n I were only trying 2 months and just got our BFP. We have 2 girls just turned 3&5. They're amazing a lil energetic but so much fun. Anyway I thought I was totally ready for this new baby but I'm feeling way more nervous now than I was w either of them. I'm worried about dividing my time between all of them and DH etc. We travel together w our family business so I don't need to worry about long hours away. That also means I will be starting older DD w homeschool next year with an infant. 
It just seems so strange to me to be having these feelings when I was so beyond prepared for our girls. Like I almost want to hold off telling my family because I don't want others to think I'm not ready? No idea why I would be thinking anyone would judge me, why should I care? I personally feel like I'm a great mom to them(not trying to brag), my hubby and mom and family tell me that often. I'll admit they can be spoiled from time to time but we have a close extended family and they often get attention from all angles hard for a mom to control all that! 
Any advice or stories? I'm sure there's many of you out there w three or more young ones and they have turned out great! Thanks for reading sorry so long, guess my prego brain has me worrying.