SD5, unexpected spotting!

Today marks the last day of 7.5mg letrozole. My mood was good until i found some brownish spotting on my pantyliner in the afternoon. I thought it was some vaginal shed off due to our morning baby dance, somehow the spotting becames fresh red colour. I was so worried and doubted shall i continue with injection tomorrow, so i talked to one of the infertility staff. She said it might be the leftover of my period?! Erm, not convincing at all. My period completely gone for almost a week! I tried to google, seems like some of the people did have some bleeding after letrozole. Ok, i will still monitor if the spotting become heavy. If it did, i need to head over to the hospital a day earlier than planned.

Updated: It did getting heavier for the following two days, almost likes medium flow of period. Thanks God, it stopped on SD9.