Did we start out with more planets in our solar system during the early formation?

Current theory has several planets ejected by Jupiter's gravity, plus a Mars size planet which made a grazing collision with Earth.  The ejecta became our Moon, while the main body was incorporated into Earth.

That is the current theory, that there were several other planets (likely ice giants like Neptune and Uranus) that were ejected from the solar system due to the migration of Jupiter and Saturn around 2 million years after the solar system formed.

Yes... The nebula that our solar system formed from started with countless small bits that collided & stuck, building up over time... 

  Hundreds of planetoids became dozens, then tens, then down to the 8 planets we know today.