I think it is kind of a normal and ongoing transition to deal with these feelings while staying at home with your children. If you are not careful, you will lose a part of yourself-and the partner who 'goes to work' just doesn't get it, because they can only see that you get to 'sit' home all day. While it certainly beats getting up every morning to 'go to work', it can be a very isolating experience.
Now....I am learning that while it's not supposed to be the best way to handle things, taking a passive-aggressive action plan is really working around here. I felt I was wasting my breath, trying to explain my feelings to him, and and he wasn't all that interested, and was getting tired of my nagging. Now, when I get feeling down about his attitude, I find a creative way to get my point across.
In your shoes, I would lock on the fitness comment, and use it as a great opening to do something nice for myself. However, I wouldn't work out on the ET in the basement, which would be further isolating, I would join Weight Watchers, or a gym so that I could go out of the house to get my socialization time, while he sits at home with the kids. Really, by telling you to 'deal with it', he is giving you a free reign to do whatever it takes to make you feel better.
As far as your feelings for him are concerned, I believe that focusing on your physical and emotional well-being might improve your outlook. It sounds like you are not happy, and somehow are depending on him to fix that-but most men are incapable of nurturing us the way we need it--so you must nurture yourself.