Probably my imagination, but...

My period ended this past Saturday. These past two days, I get great sleep at night, and by 10 or 11 the next day, I'm having to fight to stay awake. I feel like if I shut my eyes for 2 seconds, I'm going to fall asleep and sleep for hours. I woke up with a fever this morning also, and have felt so "blahh" today. Am I just tired, or could it mean something else?! I can't help but look at every little thing because my husband and I have been trying for almost 2 years now..