Best time to start taking mucinex?

Amber • After a long journey finally had our beautiful little girl! She is a year old now and we are ready to try for baby #2!
So trying out the mucinex thing this month. I noticed last month I never had EWCM and thought this may help to try this month but not sure when in my cycle is best to start taking it. Last month I didn't Ovulate till cd 18 do I wait a few days before ovulation? Any advice on this would be great! Thanks ladies! :)