Scared - need advice

My last period was the 5th. I have breast augmentation surgery February 5th and I stupidly slept with someone drunk and he pulled out this past Saturday night into Sunday early am (18th) - I was due to ovulate the 21st. I took plan b Sunday evening so about 17/18 hours after the unprotected sex. I took an ovulation test around the same time and it was positive. What are the chances of getting pregnant with pull out and using plan b? I’m super nervous.