Belly aches early pregnancy?

Is it normal to have belly aches in early pregnancy? This is my second pregnancy (first pregnancy was a blighted ovum and HCG did not double fast at all) this pregnancy, my HCG is doubling about every 24-30 hours. I found out at 3weeks 2 days. I am now 4 weeks 3 days. I have been having aches and a sore back (like it needs to be cracked). The pain is very mild, but uncomfortable is located by my belly button. Any insight? Is this normal?