Weight gain?

Kathryn • Hello everyone, my name is Kathryn and my fiancé and I are trying for baby number 2. We have a 4 year old daughter
Swear I am losing it. Was looking in the mirror tonight and notice I had s belly. Haven't changed my eating habit or anything. 2 months ago right before my cycle I had tons of pregnancy like symptoms and then my period came. Even though it was normal for first day or 2 and the retest was light which sometimes I happen I shrugged it off. The picture on the left is when I was like like 15 weeks with my daughter and the left I'm not pregnant that I know of but they look such alike only difference is picture on right my top of my stomach sits out further. Am I just gaining weight??