Go to your doctor and request blood tests. Have your Vitamin D, thyroid, fasting blood sugar levels tested. Also, it wouldn't hurt to have a three hour glucose tolerance test done.
Vit D deficiency will make you feel "blah" about the world. Thyroid issues will mimic depression in certain cases.
You'll read that online, and I can vouch for its accuracy.
If you're only talking with your hubby daily, that may be adding to the feelings of isolation. When it warms up, take the kids to the park and strike up conversation with some of the other moms there. (If you're on a tight budget, that one's no cost!!) Consider joining a book of the month club or a dinner club of some sort--they're just excuses to ditch the kids and the hubby for an evening or two a month.