If he came on your pants only like a wipe and you were on birth control and on your peirod and bad a tampon in should you be worried?

You shouldn't be worried about pregnancy or STI/STD risk, you should however be worried about your complete lack of understanding about how conception occurs. Semen would have to get into your vagina, not on your pants, in order for you to fall pregnant and while you're on birth control even then pregnancy risk is minimal. Tampon or not, period or not, makes no difference here.
No,because the tampon was blocking it.