22 weeks pregnant and numbness

I am currently 22 weeks and 2 days pregnant with a little girl. This morning I woke up with back pain and than my butt would get numb and it would continue down my right leg and a little down left. It kind of feels like when you sit in one position to long and you leg goes to sleep. It was very uncomfortable. This continues for most of the morning but has eased up as of now. Is this normal or should I be concerned? What are some good ways to help it?