I dont think it is too early for any kind of sickness!! I remember sitting at my computer at 2dpo and I was feeling slightly nauseous. And if I let myself get too hungry during to TWW I would get nauseous too. And I know that they do say "morning sickness" but I think the sickness can happen at any time!! I feel my worst in the afternoons and especially at dinner time (I have not eaten a nice healthy dinner for a few weeks now!)