So tired but can't sleep!

Is anyone else going through this? I am only 7 weeks and feeling exhausted. I am constantly yawning and feeling so sleepy throughout the day and early hours of the night. When I go to bed (between 9 -9:30) I lie there unable to fall asleep for at least an hour. When I do finally fall asleep, it's only for a few hours and then I wake up without reason to start the whole process over. It happens 3 to 4 times a night, sometimes more. I am not taking naps during the day either so I know it's not because I am sleeping too much. Any suggestions or advice. I am dying for just a full nights sleep. Thank you so much in advance.