Sounds normal to me. Swap file is your issue. It can range as much as a GB or more. As it gets smaller, you get more space. As it gets bigger...
Dr. Watson is from a system crash. It will re-write itself again next time your computer has a problem.
No need to panic however. Delete some stuff already!
-S
PS. You can set a maximum swap file size by the way. If you have 3 GB or more, you can even turn it off safely, though some apps expect it and will require one be present.
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