I was very similar hun in the first trimester as i explained to my Midwife at my booking in appointment. She Booked me in for a few more checks just to keep an eye on me but if you are woried than talk to your midwife. I'm sure it's quite normal for you but it's always nice to hear it from a professional
Jools my sister always loses a stone in the 1st mth and think its normal like the others say.
I agree with caroline on the feeling faint think,may be snack in between meals will help as the increased blood flow to placentre is to blame.