4 weeks

So I'm about 4 weeks (counting from last period) and I am having the worst back pain! I never had this with my daughter until much later. It's driving me crazy! I had no symptoms with my daughter until 8 weeks (that's how I knew I was pregnant). Is this normal this early? I had positive test as early as 9 days after ovulation. So I think the hormones are strong with this one!