Help please.... Cm and ovulation days

Right I don't mean to be gross or anything and maybe a bit too much information... In the lead up to ovulation day and we are supposed to be checking for fertile cm, I don't have a clue what I'm looking for sometimes because if myself and partner have had sex then how do you tell the difference between cm and semen?? Obviously after sex you do have some 'leakage' for a while...  Please don't let me be the only one that doesn't know this!! Lol.