I'm getting weaker by the day and i'm wondering what is happening to me.

Started from a few days back. My knees can barely support my body and they keep giving ways when i walk. Feeling very lethargic. Very Very worn out. The doctor didn't say anything much about it. Adviced me to stop doing my sports and have tons of rest. Sigh... think i'm really going to give up dancing after NDP until all my injuries are recovered. think imma end here. really tired.