For about a month) sharp cramping headache, feeling of fluid moving around inside head, difficulty thinking clearly. weak arms/legs any suggestions?

New headache or old?: One issue about headaches- if they are new, they deserve to be evaluated. If they are old, they may be a common kind of headache. Evaluation should include and interview and physical exam. Often if it is a good idea to consider imaging, such as MRI. The sense of moving fluid is not normally a bad sign, but weakness may be important.