I was really hungry the first few weeks and then became nauseous and my appetite has not recovered yet (17 weeks). By week 8 I had gained half a stone but subsequently lost 2lbs of it and no more weight gain so far so try not to panic!
Go with the flow (within reason). Some days I'm ravenous, others not. Some days all I want is cake, others salad. It all balances out and so long as you're sensible you shouldn't gain masses of weight.
In both my pregnancies, I haven't had any nausea or morning sickness -- at all. BUT I have been ravenous for the first trimester. I think it is hormonal, and it seems to ease up around the time morning sickness would. It seems like morning sickness in the sense that it totally takes control of my food intake.
At the start of this pregnancy (19 weeks) I kind of thought I should try not to get as ENORMOUS as I did last time, but then the hunger started and there was nothing I can do. I feel really bad if I let myself get too hungry.
Now it's OK though -- I was out shopping this morning and realized I hadn't eaten breakfast in the rush to the doctor's -- this could never have happened before!