milk thistle and birth control

I've been on TriSprintec for almost 6 months now. can I take milk thistle supplement for my liver or will that affect the BC? I'm on my third week of BC now and getting my period next week so I was thinking to just not be active til I start my new pack and take the milk thistle just up until I'm gonna start the BC or could that still have an affect on getting pregnant? I'm not going to the doctor to ask til next month so i figured I'd just post here and see if anyone has some info