In the past 3 months my left eye has hemouraged suddenly. no coughing or sneezing or high bp. i have hyperventilation syndrome. whats causing this?

?: By hemorrhaged, do you mean you got a red spot in the white of your eye (a scleral hemorrhage)? This occurs spontaneously and is not harmful or predictive of a systemic illness. If by hemorrhage, you mean a retinal or vitreous hemorrhage (with diminished vision) it's much more serious and requires evaluation by an eye doctor (ophthalmologist).

Thin blood vessel: I am guessing that you have a subconjunctival hemorrhage - bleeding under the thin, transparent lining over the white sclera. These are frequently spontaneous but can occur with sneezing, etc. They are usually benign unless they signify a blood clotting problem. If there is no bruising or bleeding elsewhere in your body, then you probably have the spontaneous and benign form.