Belly changing sizes

Dana ☀️ • 32. Married 7.12.13 • Mommy to Elliott 👧🏼 3.5.16. Due with baby girl #2 12.12.18
So for the last week or so I thought that my belly had really "popped" out.  But, today it seems to be smaller, my husband even noticed it this evening.  Is this normal?  I am kinda freaked out by this...