Any suggestions for improvements are more than welcome.

I think you have this spell last longer and have it do the damage when you are casting other spells with somatic components.

This spell is only a cantrip, with the same amount of damage as ray of frost.  2d4 damage is nothing to sneeze at, and it scales well too.

Do you know how to make a homebrew spell accurately scale with player level? Thanks. 

First, make sure you have the level scaling box checked, and that you selected the right option.

Then, to actually scale it, you have to make a different scaling entry for each level.  You'd have to make a separate one for 5, 11, and 17.

For example, on this one I had to make two scaling factors, one for each instance of damage.  I had the first one do increased count, and set the dice to 2d4.  This would pretty much be repeated throughout.

Feel free to PM me if this isn't clear enough.

Why a Con save instead of a Wis save? O.o

I figured it was sort of a physical pain caused by the words.  Wisdom would also work.

Fair enough. It immediately made me think of Vicious Mockery which is why I thought to ask about the Wisdom save. I don't think there's anything wrong with the Con save, was just interested in your thoughts.