Do you have a Tri bike? If you do, this may be OK. You should be spending the bulk (if not all) of your time in the aero position. In this case, you would typically be resting on your forearms with your bicep/tricep part of the arm as your support. This is a very comfortable position.

If you have a road bike, you may be stretched out too far. You could slide your saddle forward some to close down the angle.

The best thing is to not wait for a final fit. Get it fitted now. Id did and it makes a world of difference.