Charting is probably more for people who have trouble TTC.. Even though my cycles are regular my O day varies, which makes my luteal phase vary.. A short luteal phase can be the reason for not falling pregnant, which was my case.. That and further BT's showed that when I did O my eggs were too immature to be fertilised. Hence the clomid. It makes me O earlier lengthening my LP and stimulates the ovaries so my eggs are mature..