It sounds like you know what you need to do to "find" yourself and feel better. It is so hard to find time for exercise and friends when you have kids who need so much of your time. It would help if you had a partner at home to watch the kids while you went to the gym...can you hire a babysitter? Have a friend you can trade "kid free time" with?
You have to carve out time when you are a mom, a worker and a partner...you can't wait to find it, you never will have it. Would exercise help your tiredness?
It got easier for me when my children were middle school aged. Their activities increased some, but on days when they had no activities, they could stay home by themselves while I went to the gym.
I think it is hard to be more active this time of year. It's dark out and we want to stay indoors. Maybe we need more sleep this time of year...isn't that what humans did before electricity...go to sleep when it got too dark to see?