I don't know if this is intentional or not but the size of that bevel thing is quite big. It looks bubbly because the highlight and shadow would only be that big if it was a really "bubbly" shape. If we look at it in perspective it would be like this:
Because it's showing that there's a big curve outward/inward which can only be there if it's a shape like this.
So... make those smaller if you don't want it to be like that, and also add a bit of an outline because there is always a bit less light around the edges of two touching parts. But don't use drop shadow unless you want to make it look like it's floating.