Get dizziness and bad frontal headache everytime i stand up. i do have low blood pressure. but could this be symptoms of something serious ?

Better with lying?: If it is completely better with lying down, it may be a symptom of intracranial hypotension. While this is not a serious condition, it is a problem with have a headache whenever you stand. It it is definitely positional in nature, you will want to explain this to a doctor who can see you in person and help you get the right treatment for it. It is probably not caused by your blood pressure.