The ending of my relationship that got me there happened late August/early September.
I am sorry you are feeling this way, but I see so much of my own experience in what you are posting.
I am originally from New England and fall is my favorite time of year. I live out west and have for 18 years (which I LOVE every other weather condition). The ONLY year I did not get homesick in the fall was the year my breakup happened. I just did not have room.
Part of how I knew I was getting better was when I could appreciate a fall day, or a sunset, or birds singing. The fact that you can even see the leaves is further along then I was at this stage of things.