why am i showing already? (1st pregnancy) could it be twins?

CJ - Our 1st mocha baby due Dec `18 🍼👶🏽💕

i am not super skinny, more athletic build. i am continuing to exercise 5 days a week. however, i am rapidly starting to show! my jeans are tight already and this is shocking that Ive gained 10lbs already! im only 7w/3d...ps my 48Hr hcg quadrupled....is anyone else showing?