Skyrim lag help please!

KieranDavidW123

Honorable
Apr 28, 2013
532
1
11,060
I have been having issues with noticeable lag on skyrim. I just be playing on high settings without noticeable lag aka 30-35fps.
here is my rig:

Intel core i3 2120 3.33GHz W/Hyperthreading
4GB DDR3 600MHz
XFX pro core edition 550w
Nvidia GeForce GT 640 2gb GDDR3

I now play on Medium settings and in outside areas and in cities, I am left with a very annoying 30-40 fps, It may sound like a good fps but when i go in first person, it looks like 25-30 fps but it says 35-40 fps. Even when I play in 3rd person I am left with annoying lag like this, it says 35-40fps but it looks like 30fps.

I Play on 1920x1080. it didn't lag like this at the start, it was smooth at 40fps and looked like 40fps whether as now it says 40fps but it looks like 25 or 30fps. I would really like a fix for this any ideas?