Recurring nightmares like that usually point to stress or anxiety that your brain's basically processing while you sleep - falling dreams are super common when you're dealing with something that feels out of control in waking life. The fact that it's happening multiple times a week and disrupting your sleep is worth taking seriously; I'd honestly suggest talking to a doctor or therapist about what's going on, since they can help figure out if there's an underlying issue (anxiety, sleep disorder, whatever) that's triggering it. Sometimes it also helps to journal before bed about what's stressing you out, which I started doing on my morning runs when my mind was racing, but in your case writing it down at night might help your brain process things differently. If you keep hitting a wall with the bedtime routine changes, professional help will probably be more effective than tweaking when you sleep.