It's normal
It's just your uterus stretching and preparing itself. Yep it starts quite early. That's why we all keep expecting AF to arrive.
As long as the pains aren't terribly painful or accompanied with blood then there's nothing to worry about.
You'll find lots of little aches and cramps rise. They get quite spooky at times but just remember it is just your body adapting.
Back aches I never had so early. I'm getting it now at 11-12 weeks. Like muscle aches almost. But I'm getting them across my tummy too.
EDIT: Sorry just reread your post and wanted to add. Ectopic pregnancies I obsessed about before my first scans. Apparently the pain gets worse and in bad cases it's unbareable and can be accompanied with blood. Also it's more to one side.
However pain in the side of your abdomen doesn't mean it's a ectopic pregnancy. I got that too. Quite a sharp pain. It was never severe but it scared me to no end.
I'll stick to my original advise though. As long as it isn't accompanied by blood or isn't severe it's fine. Period type cramps aren't a cause for concern at all.
Congrats on your pregnancy and all the best!