I've always had back pain from really early on. If it feels more like period pain, that's more of a warning sign, but pregnancy comes with such a variety of odd pains and symptoms that there's no need to panic at this stage... And morning sickness would point more to a healthy baby than a miscarriage, so that's a good sign :)
I had lower back pain with my first it's probably the hormones loosening your joints and your uterus growing. The strong nausea is a good thing that means your hormones are rising like they should. It all sounds normal to me but if you're concerned call your Dr.