Std possibility that seems impossible. i have what appears to be genital herpes although the circumstances required to have obtained it are implausible. i've been in three sexual relationships, all committed, all months apart. my current relationship is 1

You : You need to have these cultured and tested. There are other possibilities besides std, especially if you had a cut. After a cut, MRSA (methicillin resistant staph aureus) can occur and also looks like sores for example. Please be seen immediately and have cultures taken so that you know for sure and can receive proper treatment.

Not implausible...: Dr. Engrav is correct, i.e. be certain the diagnosis is accurate. Assuming it is, there's still nothing "implausible" in this situation. Genital herpes is often acquired or first diagnosed in mutually committed relationships, often only after years of regular unprotected sex. You could have had it a long time, without symptoms until recently. Or one of your partners was unknowingly infected.