Is this normal???????????????????

No, I don't think that's normal. Your step-mum needs to lay off a bit. What's normal is wanting to rest for a few minutes between coming home and moving onto the next chore. What happens when you try to ignore her? And have you tried discussing with your father the way she treats you? I would let him know that you're more than happy to help out with the household chores, and you don't intend to neglect them, but that you're capable of doing them on your own time and without being yelled at so rudely and with such a patronising and unsympathetic tone.