My team told me gentle walking only till my six week check, then from there I was told to gradually build up exercise. Don't forget you are consuming so few calories at your stage that too much physical effort could cause a problem for you, and of course your body needs time to heal properly.
I was back at the gym at about three months post op, but found it too much as I was not able to eat enough calories. I have since had a stretch and do cycling, swimming, gym etc.