are you CM or cervix checking.
i'm on a fertility programme at the minute that is all cm checking. you need to check cm before and after you shower as any messing down there can wash away your cm.
also there is a method called bear down that my fertility nurse tells me to do if we decide to dtd and it's not quite ovulation time. sorry for all the tmi, kinda gross, but after you have dtd, preferably within 30 mins urinate and do the action as if you are having a bowel movement, that way in theory all the remaining

should come out and shouldn't really interfere with your CM. if you wait 10 mins before doing this all the

should have had chance to reach high enough up.
if your just cervix checking sorry for all the long winded message
xx best of luck