Why have I been so tired last few months?

I've been going to doctors off and on over last several months. I've done blood work and no one can explain why Im so tired. I've done pregnancy tests thinking I am pregnant but that was negative also. I do work long shifts anywhere from 11-12 hours a day. I get home from work and want to just lay down. I shower eat dinner and when I put my son to bed I fall asleep than too. I cant really have a social life cause Im too tired. When I do get to have time with my bf I usually fall asleep during a movie. I noticed recently that when I wake up in the morning I feel like I've taken Benadryl and it hasn't worn off and I feel groggy. Does anyone have any ideas? I don't know where to turn to next. I live in a somewhat small town without a lot of access to specialists and plus with a long work schedule going to the doctors is difficult.