My 3GS has gone crazy

I have a 3Gs that has gone crazy. Out of a sudden, voice control starts, plays music and even makes calls sometimes, the phone starts switching between applications (closes and opens them) and I can't do anything to stop it even when I touch the cancel button. It does this over and over again. At the same time this problem happened, the home button stopped working. Well it works sometimes when I restart the phone but not always. I don't think it's a matter of pressing the button hard because when it works, it's always the same press I use as before.
I upgraded to iOS4 but the problem still exists. I hope someone out there can give a hand.
Thanks