You are right in the context that orbit is not circle. Mathematically for circle eccentricity e = 0 but for earth orbit it is very small, that is closer to 0. Secondly you do not understand motion under force or simulated mechanism. For example, take a circular rim, consider a point on its diameter, (not on center and neither on periphery. Now tie a ball with elastic (spring nature) string, one end of string fixed to that point on diameter and another to the ball on rim periphery. Now move the ball to cover the entire circle of rim. This is circular motion with different perihelion and aphelion with respect to that point. So in general your showing your lack of maths. But then we know what you know about sphere volume. Don't we?