I some times feel like some kind of pressure in my head(mostly the top) and its not a pain. i wonder if it could be dangerous? by the way its not new

Difficult to Answer: One of the difficulties in neurology is getting enough information, and in this situation I do not feel I have enough to offer a diagnosis. A pressure sensation could represent a tension headache, an atypical migraine, or actually be the result of mild increased intracranial pressure (very unusual). I would discuss it with your primary doctor or make an appointment with a neurologist.

....: given your age and symptoms, appears that it may be stress related. if you experience dizziness, nausea, problems with balance- please see your health care provider for a CT scan. best health.

HA's are common: Although the cause of yours could be triggered by sinus issues, could also be secondary to jaw/dentition, neck, even reactions to medication or diet. Some varieties of migraine act this way. Seriously doubt "it could be dangerous".