I took st Johns Wort for a month once a day, then stopped a few weeks ago and have taken it only twice a week(when I remember) I have been on birth control for 2 years and I was wondering if this small dose of 300mg would interfere with it and I could become pregnant? I was active on Sunday (55 hours ago) and took plan B today to be safe, but it can interfere with this to? Thank you.