I would run a couple of tests for vitamins and minerals. Certain deficiencies can make you feel drained. For instance, the lack of iron and vitamin B12 can really take the wind out of your sails. You could be eating like a horse, but make sure you are eating the right food. But sometimes despite eating the right food, your body (due to end number of reasons) does not absorb nutrients properly. Also run tests for sugar and salt levels. An imbalance here can also make you feel weak. Have you been through an emotional trauma recently, like a break up or the loss of someone you love? That can also take a toll on your energy. Sometimes making you sleep more than you should. If so, take your time to grieve and find a way to let go and move on.
If there are deficiencies then do take supplements as prescribed by your doctor and take some of the advice given to you on this forum. Most of it is good advice