It depends. Do you mean that you worked two weeks (14 days) consecutively without any breaks - you worked every day?
If so, then "I have been working for two weeks with no weekend breaks."
Or do you mean that you worked for two weeks (14 days) but without working any weekends - you worked for two weeks but you didn't work the Saturday or Sunday of either week?
If so, then "I have been working for two weeks but without working any weekends."