Sub stopped working, unless i push on it?

sounds like maybe the wiring from the cone to the magnet is ripped or broken.... which is why when you push the cone in it works because it pushes it far enough to make the wires touch just barely, but when you let it go the wires seperate and you get no sound.

Your wire is built with slack, so when the cone goes in and out during a song, the wire can move with it and not get broken. but when you cone moves too in or too far out, then that wire can snap or become disconnected.

I have fixed this by soldering the copper wire, but you may lose some power because your copper wire might be a bit shorter(it will probly break again)... or you can lengthen it, but it is not easy to solder... some places will fix it for you but the cost may be more than what it is worth.

This is just a guess, take your speaker outta the box, and look to see if these wires are broken, lose, or frayed.

good luck.