Is it normal to have a fear of getting stabbed in the pit of your arm?

I have this deep seated fear that while I'm asleep, someone (nobody specific) will come up and stab my armpit, causing me to bleed out and die a horrible, painful death. Even sleeping next to my girlfriend doesn't do away with it, and I'm far too embarrassed to admit it to her. But truth be told, I always tuck something be it the comforter, my blanket, a small pillow into the exposed pit depending on what side I'm sleeping on. Idk what I think that'll do, but as soon as I feel a slight breeze hit my exposed armpit, I no longer feel safe and cannot go back to sleep without a protective layer in third pit gap.