Clarify the timeline and commitment
State when each relationship began, what exclusivity was discussed, and what information you withheld. Do not use the absence of a label to excuse an expectation you deliberately encouraged.
Address consent and health directly
Share facts relevant to sexual health and informed choices, and obtain appropriate testing or medical guidance. Protect the other person's privacy while correcting deception.
Accept the relationship consequence
Apologize for the promise, implication, or dishonesty you controlled. Do not ask either person to compete, wait, or comfort you while you decide what you want.