You need a project that you can get excited about. I don't know if this is the solution for you, but I'm currently all gung-ho about my Fitbit. Every day I write down the numbers, and try to top yesterday's numbers. It's like a game I'm playing with myself, to get more steps in. (The numbers I'm looking at are steps, calorie burn, calories logged -- things like that).
I'm also feeling a bit trapped right now -- my kids are grown, but I'm under pressure to finish my Masters Thesis. I feel like I have to strap myself to the chair, and can't allow myself to go out until it's done. (Silly --- even when I'm not working on it, I feel like I *should* work on it, and shouldn't leave the apartment).
So it's helped a lot to have something active I can do to distract myself and make me feel good when I'm not writing and trying to concentrate! Otherwise, I'd do it with food. This gives me an incentive to do the opposite -- I can eat food, of course, but I want to keep the calories burned higher than the calories eaten (but not over 1,000, because then I'd feel weak).
I just love this little gadget. It's the best $100 I ever spent. I've lost the 30 lbs I've been struggling to lose for 25 years.
Everyone's solution is different, so I hope you find what works for you. I stayed home with my kids, too, and I remember how cooped up I felt sometimes.