onMessage is called when a message is available. you won't have a message called until the previous one was finished. So... that means no.. you will only receive another message when you have finished processing the previous one.
A continuation to this question is my question posted in this link about queue size...since every message is read in succession the size of queue should decrease in a decresing counter....but it seems that it doesnt happen so if i read the queue size in every on message .....any explanantion to this. ?