Welcome to SP--you're off to a great start here. Keep posting and tracking daily. Setting up your own Spark page so we can get to know you is a great help. And remember, we're all in this together. We help one another to get to the goal of a healthy weight and lifestyle. Together WE CAN DO IT!!
It's hard to say what it might be and I'm not a professional, but I have had depression on and off years ago--mostly when I was trying to do way too much. It sounds like you are kind of in that place now--possibly some of it beyond your control, but maybe there are some things you could let go of a bit. Even with your son's needs and taking care of your family and home full-time, you need to put yourself FIRST once in awhile. That's a really tough lesson for most moms to learn and put into practice. We need to love ourselves and realize that God doesn't want you to be that exhausted; he wants you to be joyful. So when's the last time you were truly joyful? Is there a friend or family member who could spend a night with your kids so you and your husband could get away? Even a one-night mini-vacation at a resort or nice hotel nearby can charge your batteries again. And if there's nobody to fill in, maybe your husband could take over for a couple of days so you could get away on your own (I took a 3 day trip once just to visit a friend and I was amazed at how invigorating that was). Your personal tank is on empty and you aren't helping your family by trying to keep running when there's nothing left in you anyway. You need a vacation from being the full time mom and homemaker--even if you really love it and enjoy your role. I totally loved being wife and mom, but a couple of times I had to simply put it all aside for a few days and feel free as a bird just to take care of ME. I think it sounds like the same kind of thing would do wonders for you too. In the meantime, I'll keep you in my prayers, and I hope you give it a try.