I used to sleep with the Radio on. On a couple of mornings I remember waking up in silence and thinking "why isn't the radio on?". As soon as I thought about it, my hearing turned itself back on, and I could suddenly hear the radio again. It seems that your (or at least my) brain is very good at tuning out extraneous noise during sleep.

I'm not sure that nomadic Paleolithic (wo)man would often have found a perfectly quite place to sleep (and hence the tuning out ability). Maybe we didn't evolve to sleep in a quiet environment.

Might just be a coincidence though...

Paleo people would sleep lightly so that they could hear the things creeping up on them to kill and eat them.

Hmmm, I've found that having my earplugs in at night leaves me feeling more rested in the morning, as I'm not being wakened by every little noise in the house (nor the occasional jolting snort from my boyfriend lying next to me). The sound of my own breathing acts as "white noise" and I tend to drop off to sleep quickly. I started wearing them because of my parakeets waking me up so early on the weekends.

Maybe it's an internal issue with the ear. Ear plug use can lead to ear infections.

Could be pressure to your inner ear caused by the portion of the earplug sticking out. Try cutting that part of the earplug off. I hope you get better sleep.