As you add electrons to an energy level, without adding more protons are there more or less repulsive
forces between the electrons?

There will be more repulsive force between the electrons.

Explanation:

Electrons contain negative charge.As a result the electron will repulse another adjacent negatively charged electron.

   According to the given question addition of electrons to en energy level without adding more protons will increase the overall negative charge in the the energy level in which the electrons are added.

  This ultimately leads to generate more repulsive force between the electrons.