I found it very reassuring when my doctor told me that it's actually a good sign! It's just a sign that everything is working as it should, some people aren't lucky enough to feel it growing and hurting so feel a little less pregnant and sure of it.
I've had cramping on and off the whole way through, at certain points due to growth spurts. One day I'll have a lot of aching and the next I'll wake up and my belly seems bigger, just like that.
Though, I've recently discovered the joys of Braxton Hicks! Also achey, but for no good reason. Haha.