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.
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 :)