High-end PC lag

Hello everyone, I recently bought a new computer, these are the specs:

GTX970
i5-6600K
8GB RAM
Windows 10

Anyways, I have been experiencing fps drops to the 40-50 area ever since I bought the new computer. Is there something wrong with the wow client that cause this lag, or is it something from my side?

Do you play WotLK? If so, try lowering your shadows.

Yes, I am playing on wotlk; So shadows is the one thing being bad optimized.