Is this normal at 5 weeks?

I found out I was pregnant last week, I've worked out I'm about 5 weeks roughly, I spoke to doctor as and in 3 weeks i see the midwife..

Today I was cleaning, doing normal household chores and my back was in absolute agony, I also had slight cramps so I sat down and it's eased I had to stop and hubby had to take over. Surely this isn't normal so early? is it? have any of you girls had this so early? I've had a miscarriage last year and I'm petrified it'll happen again, i am going to call doctor tomorrow about it. I keep going to the toilet to check I'm not bleeding, which I'm not.

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