Well first off to say I'm terrible with bikes.
I recently went off a curb and heard a louder than normal noise from my chain area. Whenever I back pedal the chain becomes extremely lose and practically comes off the cog and changes gear when I start cycling forward. As well as this when I push the bike the pedals move forward which never used to happen untill I went off this curb.
I can't really explain it since I have no clue what I'm talking about :x