The August 7th due date is correct for your LMP on October 30. To be clear, your period STARTED on October 30?
If so, you had sex on days 11, 12, 13, 14, and 16 with your boyfriend and on day 15 with someone else.
You'd normally ovulate between days 11 and 16 of your cycle. Sperm can survive about 5 days.
You need a DNA test. It could be either of them.