I have a question.

Im wondering if someone could give me some advice or help.

I have the implanon rod as a contraceptive...

Though I have been taking st johns wort as I just found out that it an stop the rod from working...

My bf an i had sex about 3 days a go i had just finishes my period... im a little worried that I could have fallen pregnant.... how likely is it that I could have fallen pregnant .... help ?