HELP!

I am on my period (day 3) very light bleeding, which is normal. But I have never been so fatigued in my life. I wake up around 9am to go to class, come back around lunch time and eat. After this I am so exhausted I feel like I can’t do anything else. For the past 3 or 4 days I have been sleeping from noon until 6pm. And then I can literally fall back asleep around midnight, wake up the next morning at 9am again and do the same thing all over. Any ideas what’s wrong with me?! Please help. I don’t know why I am so tired.