Chances of getting pregnant

I was due to have my period on 14th March.On 13th we made the decision that we are ready for another baby.Had unprotected sex on 13th which was a day before my period date.I have a regular 28 day cycle and I'm now 3 days late which is unusual.Do I wait before I test?I know it is too early to show up if I'm pregnant and also there is a very low chance of getting pregnant.I'm not worried but just interested to know what you all think.Anyone had same experience??