How old is your pup now?
Is he a pure malinois?
OK...usually the ears will become erect by the time they are about 10 weeks old or so...sometime is takes longer but no later than 4 months.
He may have some collie or sheltie in him...this would cause the ears to flop...the white spot on the chest and be a bit smaller :) We had a collie/shepard x that sounds just like you are describing.
Its always hard to determine a strays background. Check www.petfinder.com and type in the main breed you think he is...this will bring up mixes and you can compare pictures to what you have. We do this alot on rescue :)
Good luck and hope this helps :)