Suggest Treatment For Nausea And Extreme Tiredness

Recently I have been extremely tired and want to sleep all of the time. When I m at work, I find myself yawning all day. I ve noticed that I go to the bathroom a lot more including waking up in the middle of the night. I m eating a little more, but when I m not eating I m experiencing nausea. I m having a little pain in my lower back. I m a stomach sleeper, but it has become very uncomfortable to lay on my stomach. People keep telling me I m pregnant, but I have been having a menstrual every month. The last 2 were a lot shorter and lighter than normal with milder cramps, but I just wrote them off as the best periods I ve ever had. My question is can I be pregnant or is it something else?