Just needing advice, I'll be planning a month to start clomiphene. I don't not have regular periods. I just stopped taking Medroxyprogesterone and letrozole because hasn't worked after 1 year. I don't start a period on my own (thanks PCOS) I have ben keeping up with my period and it's bout every 40 to 43 days if I take letrozole. My Dr's nurse told me to take it on the 5th day regardless if I have a period or not. She isn't very nice or easy to talk to I feel like I'm both her when I ask questions, but just wondering if anyone has had this problem. When did you know to start it if u don't have regular periods? Did u count from ur last period ?