I used to have terrible nightmares, the kind that were so intense that even as I was waking up and my eyes were open I would still see what had been going on in my nightmares. Mainly it revolved around spiders or other creepy crawlies.
My counselor told me to have a bedtime routine. Always go to bed within an hour of the same time, and always do the same things before you go to sleep. I put my hair up and take a relaxing bath, with candles and peaceful music. You could read the bible, say a rosary, or even go for a walk. It doesn’t matter what you do, so long as you do it consistently. Drinking something warm, like warmed up milk or decaf tea, can also help. It also helps if you only use your bed for sleeping, but if you only have a small amount of space that might not be possible.
What really helped me was praying before bed. I’m talking laying everything out at the foot of the cross and leaving it to God. Talk to God about anything that comes to mind, worries, stresses, anger, fear, whatever. Get it all off of your chest. Once your soul is at peace and your conscience is clear, pray for undisturbed, peaceful sleep. Pray for your guardian angel to watch over you, and St. Raphael is apparently the guy to call on to help with nightmares, since your mind is sort of ‘travelling’ on it’s own while you sleep.
You also might try leaving some peaceful music on very low, maybe some worship music or something. Your subconscious is effected by what you’re watching/reading/listening to when you fall asleep. I’ve read before that praying the rosary has really helped some people with insomnia, kind of like when you were a kid and worried about having a bad dream, it was always easier to sleep with mom close by.
I hope this helps. I know how hard it can be to have to deal with something like that frequently. Let us know how it goes, and you’ll be in my prayers!