eating anxiety

I know bettas can go awhile without food, but what worries me is my little guy Dawson is not rounded at the tummy at all, and seems quite thin if you look at him from above. He is young though. I brought him home from Walmart, where he's been for a few weeks - (scary). I got him early...

Housing What size is your tank? 5.5g What temperature is your tank? 80 Does your tank have a filter? Yes Does your tank have an air stone or other type of aeration? No Is your tank heated? No What tank mates does your betta fish live with? None Food What type of food do you feed your betta...