I read on this site that: "A born-Jewish woman who has had premarital relations may marry a kohen only if all of her partners were Jewish.". How is premarital relations described in Judaism for this purpose? Is it referring to actually having sex? Does oral sex have anything to do with it?
The Shulchan Aruch uses almost the exact same wording in Even haEzer 6:9.
Please ensure that an actual qualified Rabbi is consulted and given all relevant details when seeking a ruling for a real life question.
* See Issurei Biah 1:10 et seq.