Why does my back hurt after taking Accutane for less than a week? I am taking 80mg a day.

I have been taking accutane for 5 days now. I started experiencing back pain on the third day along with dryness. I know dryness is usual but, i thought back pain, and joint pain came later. Over the past two days it has gotten increasingly worse and now i can feel it in my neck. Will this go away in a few weeks? should i be worried? (I am taking 80mg a day)