Bump too early

Pip • Pregnant with a little boy • c-section is booked for 4th July 2016 at 8am ✨
I don't get it, but I had an early scan last week which they figured out I'm 6 weeks. At 6 weeks my tummy has bloated and I can't do up my jeans, so I got something with a band for comfort. Why would I be swollen so early? 
Photo of my stomach at 6 weeks..