Parse error on input "if". What am I doing wrong?

The function labyrinth takes two numbers(x and y) as an argument and returns a char. Those chars represent a field in the labyrinth. With the code I wanted to calculate the width of a entered labyrinth.HoweverI alwas get this error:

error: parse error on input ‘if’

if (labyrinth x y == "0") ^^

breite labyrinth x y =  if (labyrinth x y == "X")
                           then do
                                y <- return(y+1)
                                breite labyrinth x y
                        if (labyrinth x y == "0")
                           then labyrinth x y