messed up calender

Julie

I just started charting my bbt and now all of a sudden my whole cycle chart changed instead of 28 days it's saying 30 days instead of 6 fertile days it shows 7 is anyone elses like this because now I'm confused it said I was due ( hopefully not) for af on April 1st the other day now it says April 5 Th or 6Th help what am I doing wrong