You didn't regenerate in the Time War, even though you tell everyone you did. You weren't born in battle after all—you stood just outside the closing Time Lock, listening to the screams of your people but unable to change anything.
You left, trying to drive their final screams out of your head. You wanted to be alone, because you knew you'd soon be tired of it. So you piloted the TARDIS to a quiet star in the fifth quadrant of the Andromeda Galaxy.
The velvet coat was still stained with blood; suddenly you couldn't stand yourself anymore.
You regenerated.