I feel big

I'm currently 8 weeks pregnant with my second baby. My intake appt and first ultrasound is on 2/24. I look like I am 4-5mos pregnant. I don't eat much because all food is unappetizing; and I can't stomach junk food. I haven't gained any weight yet, but my belly is big. What is up with this? I have read that with subsequent pregnancies your body just relaxes because it knows it's pregnant. It just seems bizarre.