Car lumbar support!

Claire
Help me ladies! I'm dying in my car! I normally do great in any sort of seating, possibly because I tend to sit up rather than leaning back against the seat, but in my car just not possible and my back is really hurting. Last week it was OK for two hours, and now this week it hurts after just half an hour of driving. Any suggestions or advice? I drive a Honda FIT if that helps.