Right, I THINK this is in the right forum!

I bought a new monitor today and hooked it up to my PC, however now I notice a difference. My old monitor displayed up to 1440, but this one goes up to 1920, and I have noticed a MASSIVE drop in performance. I used to be able to run Skyrim on high with only a minor bit of lag, occasionally, now I get lag ALL THE TIME and I can't even think about going into combat cause it gets really REALLY bad!

Is this normal to happen when you up the resolution, or could something else be the problem?

(my NEW PC isn't arriving for a couple of weeks and I really don't think I can go without gaming for that long!)

If the game is displaying at the native resolution of the monitor, then yes, that's completely normal. It just means your computer isn't powerful enough to display the game at that resolution

Lowering the graphics settings and/or lowering the game resolution would solve the problem.

When you go from processing less than 1.3 million pixels to processing more than 2 million pixels, per frame, performance is going to suffer.

Turning down AA and AF can help.

When you increase the resolution, you are making the graphics card render more pixels. It is normal to see a decrease in performance when increasing the resolution. What graphics card to you have currently?