Will I lose my music if I update my iTunes?

I haven't updated my iTunes since I first got an account back in Christmas of 2010.So I'm getting the iPhone 5 now. Do I need to update the iTunes for my iPhone 5 to properly work + get the full experience? Will I lose all my music by doing so? Because if so, then it isn't worth it.

Basically, I haven't purchased my music from iTunes, I've downloaded it from other places.
Also, will I actually being missing out if I dont update it? I heard that the new iTunes sucks anyways. So if I'm not using iTunes to buy anything, just to store music, is it okay if I don't update it?

You will not lose any of you music

Well first off you won't lose anything. To be on the safe side, follow these steps (I will try, I dont remember what itunes looked like 2 years ago): Go to File > click preferences > go to the advanced tab > then find the checkbox that says copy files to itunes media folder when adding to library. There should be a progress bar of taking all your music and copying them into your itunes folder. Then find your itunes folder (not sure how to do this on mac but on windows): Go to you music folder then just copy your entire itunes folder DONT move it just copy it and place it on your desktop (this is to make sure if you lose anything, you can just put this folder right back. Now update itunes and if everything is okay your welcome.