Naked Avocado

I haven't mentioned my avocado in a while and thought I would provide an update. My avocado is losing his leaves. He is naked, seriously. Before he had rows and rows of large leaves and now, just a tuft at the top. More leaves are sprouting out of the top, like usual, but it has never lost this many leaves. I think I made a mistake. It was too big for my front window so I moved it to the back with lots of sun but I think it may have got a draft since it is winter now. I have moved it back to the kitchen floor, since it is still too tall. Hopefully it recovers.