Again, It turned off last night and I can't turn it back on since then... and when I connect it to itunes, nothing happens.... when I connect it to wall socket, still nothing. no access to dfu too.

I would also like to mention that when I did manage to turn it on (yesterday), it took about a ...

Just now, I turned the iphone off just to check will I be able to turn it on again, and the same problem happened, I can't turn it back on

my iphone 3gs worked perfectly last night. It was plugged into my laptop the whole night and therefore was charging the whole night. and some songs were transferring.
but when I woke up, the laptop was still on, itunes were not recognizing the iphone and iphone was turned off. I tried to turn it on ...