If you’re using Multires sculpting (it looks like you do), i recommend you to use a base mesh instead of trying to model a full character from a cube.
The reason is that unlike Dyntopo sculpting in which you can add without problem new geometry, in Multires if you try to make a torso, the arms, then more out of the current neck of your head, all you will have is long faces, and even going high in multires level will not provide enough geometry in torso/arm created that way to sculpt details.
I suggest then that you :
- apply your multires and go sculpting with Dyntopo instead
- download/create a base mesh and restart your sculpt from it if you want to use multires
- use another object for your torso , will be painful to try to merge them though, boolean and multires aren’t the best friends in Blender