How do I stop these recurring nightmares?

I watched "The Walking Dead" but I don't find it scary when I'm watching it but I keep on having these really silly nightmares about zombies taking over my town and I'm running away from them and they kill my friends and family. When I'm having them I feel really scared and I wake up in a cold sweat and breathless but I'm not scared at all when I wake up. I hate having them so how can I stop them? Thanks!