Pregnancy Update: Is this supposed to happen?

I understand that you are supposed to get bigger during pregnancy, but I had no idea it would happen so fast.  I decided to take those chalkboard photos every week so that I could see how my body changed.  Here is the one from 10 weeks:

No real baby bump there

The next week, I had a wedding to go to.  None of my dresses really fit because I had filled out more everywhere.  So Matt took me to go buy a new dress.  I hated the way I looked in all of them, except one (and I still can't decide how I really feel about it). We bought it anyway and I wore it to the wedding.  I really didn't think I had changed too much, until my husband took this picture:

Where did this belly come from?

I look flat chested and have this seemingly huge belly.  Is it supposed to be that big at 11-12 weeks? Now I'm all freaked out that I'm overeating and it's all fat in there.  Someone please tell me this is normal.

I'm almost 12 weeks now and the same size as the second picture, but I'm still wondering how much weight I'm supposed to be gaining. I know over the whole pregnancy, I'm supposed to gain about 25 pounds, but I'm starting to think I'll gain more.  I just don't get it; I've been eating right and exercising.

I've been told by a couple of people that I just got the belly early and it'll stay like this for a while.  I have mixed feelings about this.  I am already nervous about carrying around a large stomach, but I feel like the one I have now just makes me look chubby, instead of pregnant.

In the end, I guess everyone has a little bit different pregnancy experience, and I won't know what happens with this one until it's over.