Why does atenolol 50mg daily make me feel out of balance and lightheaded despite bp and hr numbers being within normal range?body adjusting?

Not clear: drugs often cause symptoms that can't be explained on the basis of its main action .Its called idiosyncratic reaction that is unique to that particular person. Atenolol causes both HR and BP to drop by blocking the sympathetic stimulation And obviously it is not the reason for your problem .Yours appear to affect the vestibular system which there is no logical explanation as far as I am aware