If i'm focusing to my head and listen carefully, i can hear some kind of ultrasonic sound (hard to describe)persistently.tinnitus? or just my feeling?

Tinnitus: Tinnitus is not a disease, but a condition that can result from a wide range of underlying causes: neurological damage (multiple sclerosis), ear infections, oxidative stress, foreign objects in the ear, nasal allergies that prevent (or induce) fluid drain, wax build-up and exposure to loud sounds. Withdrawal from benzodiazepines may cause tinnitus as well.

Tinnitus: When you listen to your head like you describe, it is medically called tinnitus. If i were you i would not continually focus on this noise. It will ultimately become a nightmare to treat and there is not yet an effective treatment. So when you seem to focus on this noise do something immediately to get your attention on something else! believe me, do not focus on this noise!