Why not just do the following:

sort -c filename

If sort returns nothing, the words are sorted.  If the words are not sorted, 
sort will return something along the lines of:

sort: filename:15: disorder: abbs

You can also do the following if you just want to know if the words are 
sorted.

sort -c filename 2>/dev/null && echo Already Sorted || echo Not Sorted

I don't know the specifics of why grep is being used or the problem, but 
damn that is overkill just to find out if a list of words are sorted.

'man sort' will give you are the details for using sort.