I don't think it's lying. You have a legitimate reason to quit because of the surgery. The fact that you want to quit for other reasons really doesn't need to be anyone else's business. That having been said, I also don't think there's anything to be ashamed of. You are making a decision to be healthier and happier, and a better mom and wife. You should be proud of that. Maybe down the road you'll feel comfortable telling some close friends and family the many reasons why you want to quit - you'll know when/if the time is right.