Please help me :'(

Hey, basically my Mac has been playing up recently. It started out with my music constantly pausing unexpectedly in iTunes. Then when i had more than 1 program running ie. iTunes, Chrome and Skype, my Mac would begin to run slower. Examples: when opening iTunes sometimes i'll click play and it will crash, Skype will crash, Chrome will crash when loading Facebook, when i go to turn my sound up/down it delays and crashes.

I thought maybe its because i have so much music on my Mac, so i deleted all 25GB of it off my Mac HDD and put it onto an external HDD. But still the problem persists. Now today, Youtube videos wont play and the sound of those keep cutting out, what is wrong?!

Sometimes it will run FINE, like it has for the past 3 years!! But just recently i have been having problems. I've used my Mac literally every day for the past 3 years, maybe its just getting old?

I can also hear this little "click" noise coming from the Mac itself, its extremely faint and happens every so often.

Im hoping someone on here who knows more than me can help me and try and find me a solution, i would really appreciate it.

Thanks.

Do a Time Machine back=up now, if you haven't already done that.

After that run disk utility on the hard drive, but that clicking noise sounds like an impending hard drive failure

A new hard disk is pretty cheap, BUT GET THAT BACKUP DONE NOW

Hmmm, i don't really care what i lose to be honest, the only valuable thing i have is my music which i already have on my external HDD. I only use my Macbook for web surfing and Skyping now.

Could this be the problem, my HDD is about to fail? What are the signs of an HDD which is about to fail...

Thanks.