Post some close up pics of him, as babies the visual appearance will tell you more than their weight which only fluctuates very small amounts when they are not well and being very small you don't always get a true accurate reading. Don't force feed, but keep trying things that he might like. Many beardies like Fluker's Retaid, see if you can find some. Then ad some Oxbow Critical care supplement , from a vet or order online. That will be more nutritious than just baby food squash.
But post some pics of your baby, next to a ruler to show size.