Weight Gain Question 1st trimester

Help!! So I have a question.. I'm in my first trimester. Approx 7 1/2 weeks. (We find out on the 25th!!) I have noticed a weight gain in my belly and my belly alone. (Aside from my breasts) if I feel the bottom of my belly I can feel where it's starting to "armor up" but the rest of my belly is just big and hangs lower than normal. What should I do to fix this? I'm trying to do everything I can not to gain too much weight but keep the baby nourished. First picture (where you can see my face) is when I found out. Second is now. Any ideas?? Help!!