I found I was too tired to keep up my normal routine, even walking my daughter too school was a nightmare. My sister in law is a regular runner and she gave up after 7 weeks. I've found you only get your energy back around 15 weeks to lose it again at 28 or so weeks. Do what you can your body will let you know, get plenty of rest and be prepared to be tired in the first couple of weeks. Remember your making a baby.... not an easy task!