Frequent Nasal Bleeding Without Injury. Taking Metformin, Adderall And Xanax. Have Diabetes And ADD. What Are The Causes?

I am a 55 yr old (as of yesterday) female and once in a blue moon, when I wake up in the middle of the night to use the bathroom - upon rising my nose bleeds rather freely. It happened again last night, stopped in about 10 minutes, but it was free flowing enough to drip onto my feet , the floor, my pajama top, etc. I ve had this occur about 3-4 times over the past 3 or 4yrs. the worst being a sudden onset (I was not asleep, I was driving home from an evening event) that lasted 45 minutes. The bad one (45 min) occurred about 3+ mos ago. The only medicine I took yesterday was metformin (500mg 2x day) for type II diabetes (well managed). I do not have high blood pressure and have stopped taking a baby aspirin once a day due to stomach upsets for about a year. So I am not on any other type of blood thinner that I know of. I also take adderall for Adult Onset ADD (although I did NOT take any yesterday) and occassionally I take Xanax (1 - 2 0.05 mg) as needed for either stress or sleep, but again I did not have any yesterday. I took no sleep aid and only drank milk or water during the evening before going to bed. Why does this only occur at night?