Hi Jinkx - aw, this must be such a worry for you - I know what it’s like to have a family history that can seem like a permanent threat!
I’ve had several bouts of post menopausal bleeding (not as heavy as yours) but that turned out to be fibroids and polyps - the gynaecologist I saw said that whilst it’s not normal and needs investigation, it’s extremely common.
However, you’re not going to stop worrying until you get this re-investigated. It would seem unlikely that a sinister cause would wait over another year to happen again, BUT I think if I were you I’d go back to the doctor and tell them it’s been 23 days so far this time (you don’t want to become anemic) and tell them how worried you are and ask that they consider sending you for some further investigations. Worrying is just miserable and I’m sure if you remind them of your family history and express your reasonable concerns, they’ll be happy to refer you. Chances are it’s nothing sinister but your mind certainly needs putting at rest if nothing else! Give them a call next week, or if it’s too much, urgent care over the weekend.