I have had irregular cycles since bc. my last charted periods were 57, 35, then 43 days. i became pregnant the next cycle, when could i have concieved?

Hard to Say: One cannot use past period dates to definitively predict a future ovulation. Ovulation could have occurred any time during a two week interval or longer. All pregnant women should seek prenatal care from an experienced OB who can use an early ultrasound to help confirm your dating, but nothing can pinpoint your ovulation to a specific date. Good Luck!