Is Delayed Periods Normal Despite Stopping Duphaston When A Pregnancy Test Is Negative?

Hi My period is late by 5 days. I was On Duphaston for 10 days from the 16thday of period. I stopped it 5 days ago and still didnt get my period. I have very tender full breasts. I took a pregnancy test 4 days ago and it was negatif. I am not sure if I took it too early or if this is normal. My period is usually 26 says. Thank you