Is it normal to constantly feel little mild cramping through out the day?

Gwendolyn • I'm 28, hubby and I have our 5 year old baby girl and now expecting baby #2.. We are so excited!!!
I am 18 weeks today and lately I have been feeling mild little cramps throughout the day. I may get them more when I am tired or at work. I've been reading it's normal but who here can relate? They come and go. It's more annoying than anything. Not painful nor accompanied by any other symptom. Thanks ladies! :)