Actually, which HDD do you have Skyrim installed on? Also, this may be a silly question, but do you have the latest update/patch for Skyrim installed?
If you have Skyrim installed on your Western Digital drive, I recommend running a disk defrag utility. If that doesn't have any effect, do a full reinstallation of Skyrim and it's latest patch/update.
I would typically suggest that you defrag all your drives, HOWEVER I DO NOT know how that will respond as I have heard defragging a SSD can potentially harm it. Not sure if that applies to hybrid drives as well.
You won't harm an ssd by defragmenting it, but it is pointless.
To put it simple:
The reason why it's bad for a normal hdd to be fragmented is that if a file is fragmented on the disk, then the hdd head has to physically move around alot to read the data, causing delays.
However, an ssd doesn't have a head and has very low access time, therefore the performance is not really affected by fragmentation.