You should wait to see if you test negative by Monday. That being said if you tested positive today the chance that you will get a negative test result by Monday is slim.
Monday - if you test negative - you should call TK to cancel the flights/to have the flights removed from the PNR. Once you have recovered and have new travel dates, you call TK to rebook. You will then be asked to submit documentation for being Covid positive by feedback on the TK webpage before TK will agree to rebook free of charge. Allow up to 1 week for TK to respond to your feedback.
It has been described in other TK threads about how to deal with situations where one test Covid positive. I was in the same boat in February.