I don't have a problem with Joseph not having relations with Mary after Jesus was born. I can understand that.
But saying Mary was Immaculate because Jesus couldn't be surrounded by sin is a very dangerous path. It suggests that Jesus was not physically present on earth, since He could not be around sin (and the earth is corrupted by it).
Please turn to Luke 1:26 in your Bible and read it slowly and carefully..
Good grief, later Mary walked to see her cousin, Elizabeth. Of course she had a physical, and very holy, body and soul.