Lower back pain in early pregnancy

Are lower back pains normal during early pregnancy? This is my second child but I cannot remember experiencing backache with my first child until my final trimester. Please get back to me as I am scared of miscarrage and finding it soo hard to enjoy my pregnancy due to this, from my last period I've worked out I'm approx 5 weeks gone also I took a digital test which showed I was 2-3but the box stated that drs would work that out as 4-5 weeks, if I take a test next week and it says 3+ does this mean my baby is well as the hormone level would have risen or am I reading to far into things? Please help so confused and emotional