Why....

I feel so exhausted all the time and never have the energy to do anything! I am 7 mo PP and have a 2 year old as well. All I ever want to do is sleep. I feel like I’m a terrible mom sometimes if I don’t get outside or do something with the kids for more then 30 minutes. I am on meds and still taking prenatal vits, got my thyroid checked, everything and it’s all fine. Why do I feel like this? Would this be considered depression?