Slowdown after changing my monitor

I used to have an 18.5 inch monitor then switched to a 23 inch, My game felt so smooth before and no lag at all but after the change the game really slowed down. How can i fix this?

did you increase the game's resolution with the new monitor? if you did, that will cause performance issues if the computer can't handle it

Nope. But i did increase the monitors resolution on the desktop settings.

Changing a monitor has no performance impact. It has to be something else.

Okay so what do you think caused this?I have an Radeon HD 6790 video card.

Have you tried running the benchmark again or adjusting the in-game settings at all?

I remember having 100+ fps using Fraps, so its like 60 in 2k benchmark. Now my 2k benchmark is only 22.