Have you actually tried to record anything with any other program? Usually Skype isnt the problem here.
The lowest level test is:
or, for better quality:
arecord -f cd | aplay -f cd
This essentially pipes back the recording into the output device. Stop with ctrl-c. If this works, you have the problem upper in the food chain. Which unfortunately i dont know exactly, i am not that familiar with KDE's way of doing things.
In any case, Skype uses Pulse Audio if available. If you have it installed, you should install pavucontrol and see if the mic works in it.
If this doesnt work, you have to work with alsamixer (in terminal). That is the lowest level mixer you have - you can set mic levels etc there (basic rule is to disable mics in the playback tab, then go to the record tab and see what options you have there). It works real time so you can have it open while you do the arecord/aplay test.