Letrozole help!!

💋M
So i started my first round of letrozole on Monday Jan. 30 which was CD3 for me. By CD5, AFmy had stopped. But by Friday CD7 AF started over, and in full force! Cramping, sore nipples, back ache, the whole shabang. Has any one else experienced this?? I don't know what's "normal" since this is my first round.