I'm in the middle of trying to sort out my first guitar which used to be okish but now it buzzes over every single fret. The sound is dampened quickly because the strings hit the frets so often.

I've raised the action, adjusted the truss rod... apart from that I don't know what I can do to repair the bolt on guitar. Any idea what could be wrong with it?
It needs fret dressing then. Loads of people will do this for you. Can't name any off the top of my head, mind.
have you changed strings... it might sound silly (it did for me for a while) but when my strings get old (3+ months) the start to buzz and the lose their sustain...

of course, the frets could be worn down but that can be repaired as the person above me said
the above posts have got it i think.
all that's left to check is the frets and your strings.