I know where you are coming from, absolutely. When I start feeling like this I do think of those Moms who wish they could stay home but their circumstances do not allow them. Imagine how lost you would feel doing a job you (maybe) don't like for 8 or more hours a day while your kids are in daycare and there is no option to pursue what you like because there just aren't enough hours in the day!
For me, personally, I love to play tennis. I am not very good at it and rarely win, however, I just love playing and watching it on TV. It is a great source of joy for me and also challenges me (and frustrates me :)! I've managed to make a couple friends who also enjoy it so I get to the courts about once a week and hubbie watches the kids and makes sure he is home early enough from work for me to play.
I used to like scrapbooking for the kids, but now much prefer to make the books on a website like Shutterfly or something. It lets me be creative and give the gift of memories to my kids, because we all think we'll remember everything, but I know I won't.
Just give some things a try. Summer is a great time for this - pick up your park districts catalog and see what interests you - a sport, exercise class, creative class. It may take some trying some things you end up not liking to find something you really enjoy.
I wish you all the best.