I've been having vivid, terrifying dreams that eventually wake me up in fear (usually when I am about to die for this or that reason in each nightmare) and with my heart beating fast and a tight pain in my chest. I have nightmares often (at least once a week or every other week) throughout my life, but recently I've been having multiple nightmares every night. Sometimes the nightmares also continue if I go back to sleep too soon after waking up from it, and I would have to wake up again and again and keep myself awake for a few minutes to think about other things before going back to sleep in peace.

For example, last night I had three separate nightmares, so I woke up multiple times in fear in the middle of the night. The first one I already forgot , the second was about a tsunami, and the third was a zombie apocalypse.

I don't take any medication and I don't drink/do drugs.

I need to know the cause of these constant nightmares every night and how to stop them. I want to sleep well. I realized that I'm becoming more and more anxious and a tendency for depressed feelings during the days, and I'm assuming it's because of this (or is it the other way around?).