I'm 8 weeks and bloating some days make me look huge. That's all it is.
I was pregnant for a short time in 2010 (11wks) I started growing out of my pants at about 6 weeks because of the bloating. Nothing to worry about.
Im almost 17 weeks with my 2nd and im still not showing ive been told that you show more or sooner after the first. But everyones different. Maybe ask your doctor about it.
At 7 weeks the baby is too small to cause a real baby belly. Baby is maybe an inch long, if that. Most of the belly at this stage is retention and bloating--while it is true that women who have been pregnant might show sooner, it will not occur this early.
I think it is normal. After the 1st, things are already stretched out and many women start to show sooner. Bloating is common too which makes you look bigger. I don't think it is necessarily an indications of twins. Good luck and congrats!