Is having a severe headache over the course of two weeks warrant a cancer check?

Not necessarily. If you've never been evaluated for headaches before, then you should go see your doc for that. The indications for brain imaging include severe headache with neurological signs. You should also start keeping a headache diary. Here's a link to get you started. http://www.headaches.org/for_professionals/headache_diary definitely see your doc for this.
Not really. Cancer of brain usually does not give severe headache, but cancer elsewhere could. Cancer is not the top diagnosis for headache. Let your doctor see you and decide.