Delay in period. Supplement suddenly?

I am in ovulation induction for last 4 months. For first 3 cycles, I took letrozole 2.5mg followed by duphaston 10mg for 15 days. And period was coming after stopping duphaston. In 4th cycle as it is last cycle, so after taking letrozole, I did not take duphaston tablet. And my cycle is already delayed by 6 days, there are no pregnancy and also no period. My doctor said as I did not take duphaston this cycle after taking duphaston for 3 continuous cycles, so this has happened. She has asked to take Crina NSR 10mg for 3 days to regulate period this cycle. Is this normal? Will it affect my next cycle? And from my next cycle period will it come on time automatically as I have history of always having regular period? Please suggest. Does this irregularity happen due to stopping this progesterone supplement suddenly? Please advice.