iTunes help, please...

I clicked on iTunes yesterday and an error message comes up telling me iTunes has encountered a problem and needs to close.... send error message or dont.....

I've since tried again and again and get the same message.

I don't often use my Ipod via iTunes, I use Itunes as my main source for playing mp3's etc etc.....

I've searched my laptop for any mp3 files and zero found!

My whole lifes worth of music is stored on iTunes - have I lost it?

Help me purleeze

Tanya