Hey, theres loads of things it could be
1) steer tube is too long causing the steer tube to just tighten against the top cap.
2) Peices of headset are missing.
3) Headset cracked, broken
and loads more...but they are the common ones i doubt your forks have snapped
But the little ring that goes on the bottom of your forks may not fit your headset.
Obviously your forks could of cracked or snapped but thats very unlikely.
Your best bet is to first take the screw out the starfangle nut, and if your forks
are in line with the top of ur stem, you either need to put some spacing in or,
cut ur forks down. You havent said its stiff so it does sound like the steer needs
chopping down, your forks should tighten up enough so it doesent move no
matter what. so if ur forks are the right size and fine, take it apart and look for damage and missing parts and report back here :closedeyes:
cheers andy