So u is true u can't get pregnant right after ur period stops and how is that u can or can't ?

No: Unfortunately, this is not true. This is why the rhythm method does not work. I certainly would not rely on this for contraception. A woman can still get pregnant even though she may have just finished her period. Barrier methods and the birth control pill are far more reliable and effective.

Pregnancy: You can get pregnant at any time of your monthy cycle. If a woman has regular menstrual cycles, it is less likely to get pregnant during or right after their period. But they can still get pregnant. Ovulation typically occurs in between cycles. The rhythm method only about 75% effection. This is not a good means of preventing unwanted pregnancy.