A couple of questions first:

Is this your first plane?

Is the center of gravity correct, and maybe adjusted a little on the nose heavy end of things (but within specs)?

Have you adjusted the throws for low rates?

When you pull back on the elevator, are you adding any left aileron without knowing it?

Lastly, it looks as if the ailerons aren't set up correctly--the left one looks like it is higher than the right. That'll dip the wing for sure.