Other things to consider are (1) whether you might have added additional weight while building, perhaps beefing it up here and there, etc.; (2) is the CG correct, or (3) is the engine above or below the recommended size??

Just my $.02

What Chuck says is also true... get someone else to fly it and see what their opinion is. But, whatever you do, don't give up and don't stop building. We've all been there.

Bob