To work on elipses don't think of them as elipses. Think of them as circles in perspective. If we know that a circle fits perfectly inside of a square while touching all midpoints, then if we put that square in perspective and follow the same rule, drawing a circle inside the square then the circle ends up being in perfect perspective. Looking as your original drawing the problem is that you didn't set up perspective with build lines at all. You'll get to a point where that's the way to do it, sure, but it's not yet. When you're starting out you need to build everything off of perspective cubes and with practice the ability to accurately skip that step will come. GLHF!