my boot wont shut & central locking wont lock car?

I have a renault megane hard top convertable 55 plate all doors & boot will not lock, boot will not shut, had to drive with boot bouncing up & down & onboard computer telling me boot open but can't shut it. central locking is just clicking like its trying to lock but wont, its not my battery on key already changed that, but with boot not shutting interior light is on & my battery will go flat. Dont know what else to do? any suggestions?