My fertile dates were from the 13th through the 18th. I had sex on 11th, 13th and 15th. All unprotected. My ovulation date was on the 16th. I had another sex on the 18th. On what date of sex do I have the most chance of getting pregnant? Is it too late to take a plan B? If i do, will I still get pregnant or will it be effective. Please help