When i lay down i feel dizzy or lightheaded? what could this mean? stress maybe.

See doctor: You take Benadryl (diphenhydramine) and Lisinopril which may have additive effects in lowering blood pressure, perhaps more prominent when changing positions (?postural hypotension). Suggest you see your pcp for evaluation of meds and lightheadedness to rule out medical reasons for your symptoms. Meantime, change from standing to lying down more slowly and try to reduce your stress. I hope this helps.