When possible, a week ago, I'm very busy and relatives from other provinces came to visit and I don't have time to write a reply sent to you, and I teach, I apologize to you very seriously.
When the weekend comes, I'm very busy and relatives visiting from out of town and I do not have time to write back to you, and I'm teaching, I need you very much.
Last weekend, I am busy and relatives from the provinces to visit and I have no time to write a reply sent to you, and I teach, I want to apologize to you very much.