Hi kitten, I hope this thread helps.... it is the one ethanryan was referring to earlier!
http://www.theanswerbank.co.uk/Family/Parentin g/Question528944.html
I don't think you sound like a crap mother atall - what hours does your son go to nursery for? Could you get him to help you with preparing food for lunch / dinner? What about a sing-a-long or dancing / exercising DVD that you can do together?
My neice was such an active youngster that whatever you did to fill the day was never enough, she just wanted to move onto the next thing. One day I had her from 8am and by 2pm we had been to shop, the park (on her scooter), did some housework, painting, baked cakes and made pizzas and she still said that we hadn't done anything! Like your son, she doesn't like playing alone; but you don't hear a peep from her when she has a friend round and they are playing dressing up or tea parties. I think it would be a good idea, as annie suggests, to get a friend round to play. You never know, their mum might return the favour and you end up with some time off! XX