Randomly crying

Rachel • 24, Hull UK 🇬🇧 Expecting baby number 1, 👶👑 my little princess due 29th February
I keep randomly crying, even when I don't feel sad. 
I was reading though the cards we have received and just burst into tears. I couldn't find my socks, so I cried! Trying to explain to my SO, on the nicest possible way, that I need him to stop inviting people, I cried! 
Is it normal? My baby is 4 days old