Is it really dangerous to have 2 ct scans of head 5 and a half months apart? will it cause brain tumor like some people say?

Safe: This is well within the safe dose of radiation exposure. It is important to remember that time does not reduce the risks of exposure to more radiation. In otherwords, radiation exposure doesn't "wear off", and is cumulative over your lifetime. Best way to think about it is if the ct scan is really necessary, do it. If if not really necessary, hold off. Discuss this with your doctor to find out.