Overthinking, insomniac…

So, as I lay here in bed at almost 3 in the morning, all I can do is think about all the tasks I have to complete in the morning… I have 4 hours until I have to start getting my oldest child ready for school, and then what I will pack in his lunch… are the clothes I set out for him appropriate for the weather? To answer that question, of course not, I live in southern Indiana where the weather reaches all four seasons in a matter of hours… Once I have him taken care of them I come home and chase the toddler around the house cleaning his messes, I have dishes that need to be washed, clothes in the dryer need folded, carpets need cleaned, animals fed and watered… I can not remember if I have to work tomorrow, so there is another task to add to my ever growing list. To make all this worse, I suffer from anxiety and depression. So I get anxious over the tasks I need to complete, but my depression makes me not want to complete them. This is my cycle of life.
I envy the people who are able to sleep at the drop of a dime. This used to be me. I was a heavy sleeper. I was able to sleep through a rock concert, I fell asleep in an IMAX movie (Star Trek), but now, two children later, I feel like if an ant farts two blocks away, it wakes me up on the off-chance that I am asleep. I have gone 36 hours without being able to sleep, and that’s even after taking doctor prescribed medication one night, and melatonin the next.
I don’t understand my body, how exactly does it work that I can take melatonin one night and fall asleep (not stay asleep), but if I take it another night I am up all night, like right now. My conclusion, I am anxious. I am counting down the hours until my next task, and I am scared I won’t wake in time.. I have tried meditation, medication, teas, warm baths, music… nothing.
If anyone has any advice, I would be willing to listen. I want to sleep like a normal being again, my next option is a sleep study which honestly I am kind of scared to do, but if it can help me figure out what is going on, I should suck it up and do it!
Have a good night, and sleep well.