My computer starts to run slowly and my dwm.exe CPU usage rises when i plug in another monitor (My TV)

I currently have a Benq 24in 144hz monitor, everything is okay. Once i plug in the HDMI from my tv into my GPU for split monitors my dwm.exe CPU rises from 01 to almost 50. My computer starts to lag out and performance drops. I had to stop the process of dwm.exe to get my computer to stop lagging. I also blue screened twice with it plugged in. Could this be a GPU issue or a CPU issue?

(I have a Intel i5 6600k. And I also have a GTX 760 GPU.)