Bringing on a period?

I'm on CD 68 right now. My cycles are always between 50 - 60 days and this is the longest one in 7 cycles. I know I'm not pregnant from taking a test yesterday and the fact I never have gotten a positive opk. I have a vaginal ultrasound to check on my ovaries and uterine wall on the 21st and I'm honestly scared it's going to start right before the ultrasound and I'll have to reschedule it and have to wait for at least another month.. I'm looking if anyone has any ways to naturally bring in a period by any chance?