This is normal for me when not pregnant. I always woke up for about 30 minutes to 2 hours in the early morning hours somewhere between 3-6am. Oddly, it's all completely changed since I got pregnant, and now I sleep through the night every night (with the exception of getting up to pee 1-2 times, also normal for me pre-pregnancy though). I think being pregnant throws you for a loop and you achieve a new normal. I'm glad mine is letting me sleep a bit now, it's a really nice change, but I anticipate it may come back later on when I get a bit less comfortable. I've always found that reading in the middle of the night helped me to fall back asleep faster (I mostly read the news on my phone so don't even turn on the light). It might be worth trying. It kept me from just stressing about not sleeping which didn't help any.