If you feel "off", you are the best person to know whether you are experiencing depressive symptoms. From your desciption, I would say that's a definite yes. Depression often occurs are your children get older, and don't require the same amount of attention and constant interaction as when they were younger. Also, when you are working a job in a regular, bring home the paycheck sort of way, instead of actively pursuing an upwardly mobile career, depression could also set in. Serious medical issues, especially the ones that significantly alter your normal routine, are exceptionally good at bringing on the symptoms of depression.
I suffer from chronic moderate depression. There's test that psychiatrists/psychologists/counselors use that can diagnose just what level of depression you have. Perhaps you can take that kind of test to determine how symptomatic you are. In all the years of taking the test, I've scored exactly the same number, within 1 or 2 points every time.
I am on permanent disability, and have chronic pain issues everyday, in addition to some conditions that become acute at times. I can no longer work, my brain doesn't function up to par anymore, and I know longer can afford the lifestyle I was accustom to. I am 43, divorced, with no children. I lost my house in my divorce six years ago, so now I live in a small apartment with my three cats, about a mile from my parents. My love life is practically non-existant and will most likely stay that way.
I have lost touch with many friends over the years. They have just kind of dumped me, because with all my medical problems, nobody want to hear about my stuggles for very long. I have developed a new group of friends that "parties with a purpose", so we do lots of charity events and party in between. I love my new friends, but they are all much more affluent then me, so I can't do a lot of the "partying" events, due to a lack of expendible income. The amount of charity events I can do also depends on my medical situation. I participated in an event about a month ago, that ended up with me spending an entire week flat of my back. Not so much fun.
The root problems that cause my depression are not going away, so I'm pretty much stuck. I'm not currently in counseling, as it's never really helped me. My situation is the way it is, and no amount of talking about it will change anything.
Winter, it sounds like the things that are making you feel depressed are more from standard changes in life patterns. You have a very good chance of being able to pull out of your funk with the property medication and some counseling. Please seek out your primary care physician for a medical assessment and see if he can recommend a good counselor to help you work through the rough patches. Please let us know how you are doing.