You do not need to use all of those tenses. Your stay is for six weeks total, and you are in the midst of that period, so the present is fine.
If there are things you need to be very clear about, you can say things like "I'm two weeks into my six-week stay" or "I have four more weeks remaining in my six-week stay."
I'm here from the 18th through the 22nd.
If the entire period is not important you can say something like "I have four more weeks to go" or "I'll be here two more days."
EDITED to fix the typo on "through."
Student or Learner