(((Gotta))))
First things first..... see your Dr to make sure you are healthy that there isn't some underlying issue that is causing the exhaustion you describe. Yes our lives are super busy especially when the kids are school aged - until they start doing some driving on their own.
But the level of exhaustion and tiredness you describe seems more than that. So go have a physical. I also wonder if this isn't kinds a vicious circle phenomenon for you, you are so busy with them, you don't see your friends anymore, that makes you depressed, so you don't feel like doing anything, which just continues the cycle of not doing anything for you. And one also needs to consider if there is some underlying depression between everything that brought you here, then the miscarriages too, it would almost be expected.
Congrats on the volunteer job. I have one kid away at college, and one in the house that is in between programs for the next 6 months, and he works pt. He helps me with some chores WHEN I ASK... but never does things on his own. He is 21, and pretty much is allowed to come and go as he likes. My point is I am finding that I have more free time than I used to and have been considering doing some volunteer work at an animal shelter near our home that we have gotten most of our kitties from over the years.
When life started to settle down for me (I work full time too) and I found that I had time to myself some of the things I have done are to go back to the gym this helped me have more energy. Take classes and get SCUBA certified, we have since gotten the kids cert'd as well have done a couple of dive vacations. Other things I have done is to teach myself how to Crochet, great hobby for winter, have something warm on your lap, while you do it, and you can always watch TV or listen to music while doing it. My other latest newest thing I want to do is take some pottery classes, the Jr College near me only offers daytime classes, so I am trying to figure out if it is worth paying a studio to learn.
Also doing all the mom stuff is exhausting. Don't know if you do it all, or if you are making the kids start picking up some skills/chores along the way. My kids have been doing their own laundry since they were 7 & 9. They also were responsible for cleaning the bathroom they used, doing the cat box weekly, and feeding/watering our chickens. They also are asked to cook when home, I work full time (more than 40 hours a week) so the expectation has always been that everyone works to keep the household running. But that wasn't the sole reason to have them do those chores, it teaches them responsibility, and they know how to cook, clean and do laundry, which is more than a lot of kids these days do when they leave for school.