How soon can I get pregnant after taking accutane for 5 months?

The time it takes isotretinoin to be cleared from the body will vary from person to person. Although most of its by-products should be gone within 10 days after the last dose, the FDA recommends waiting one month before trying to conceive.

The FDA recommends that females do not get pregnant for a minimum of 30 days after stopping Accutane, no matter the dosage or time they were on it. So I'd stick with that plan. "This
answer has been solicited without seeing this patient and cannot be
held as true medical advice, but only opinion. Seek in-person treatment
with a trained medical professional for appropriate care."