How do i know that fertilization did took place

If you are referring to traditional fertilization (not in a test tube), the only way to know for sure is to have a positive pregnancy test.

Fertilization may also occur without implantation - the sperm fertilizes the egg, but the embryo does not implant in the uterus. In such case, you will never be aware that fertilization has occurred & you will get your period just like in any other cycle.

Good luck!
Rachel Inbar
www.fertilitystories.com

you count the first day of your period for ten days  and on the eleven day that is the first day of  your fertilization