Help Low on Space Errors

[Elzair]

For the last week or two I have been getting a "Low on Space" alert. I have been uninstalling unnecessary apps, moving whatever I can to the SD card, and clearing my SMS messages and call logs, but I still keep getting the message. Now I cannot even install apps from Google Market due to "insufficient space". However, the phone says internal memory has 20.17 MB of available space, and when I executed the df shell command on my root directory, this was the result:

/dev: 115612K, 0K used, 115612K available (block size 4096)
/mnt/asec: 115612K total, 0K used, 115612K available (block size 4096)
/system: 143744K total, 128984K used, 14760K available (block size 4096)
/data: 268032K total, 248620K used, 19412K available (block size 4096)
/cache: 94848K total, 9804K used, 85044K available (block size 4096)
/config: 1536K total, 1176K used, 360K available (block size 4096)
/mnt/sdcard: 15622336K total, 2357536K used, 13264800K available (block size 32768)

If it matters, I am using Android 2.2.2 on Verizon.

I should have plenty of space. What is going on?

 

[Elzair]

Update: Now it says I only have 10.88 MB. Just what is going on? Do I have some kind of malware? Should I do a factory reset, and is that done through ADB?