I am 23 weeks pregnant today. My due date is 5/20/15. I had intercourse with someone on 8/30/14. Is there a possibility that that person could be the father?

Yes, the calculation of conception date is a guesstimate based on external factors. It can be as much as 2 weeks off plus or minus. This would make 8/30 within that range.

Any sexual encounters after your last period could, potentially have resulted in conception. If you had multiple partners then a DNA test will be required to confirm paternity.