Reduced movement?

A
I'm on my way to the hospital to be checked out as I haven't felt my baby move as much today. 
He usually kicks lumps out of me but today I've only felt slight movements and even after laying down and drinking water, he's still only moving a tiny bit. I'm 35 weeks. 
I had some backache this morning and have had cramps on and off throughout the day.
Just wondering if this has happened to any of you ladies? And what the outcome was? I'm a bit worried, though I'm trying to stay calm