i am sorry about the situation,
i had a similar experience but it turned out to be a pregnancy of unknown location as they couldnt find it anywhere (no sign in tubes) but like you pos test, then bleed at 5 weeks, told m/c, hcg had droped,
went away and was still getting post tests, had bloods done 2 days later and hcg was on the up again,
they couldnt do a d and c as they couldnt see it,
they think it was an early preg, that only half m/c and that, very unusually the cells that had not fully come away had started to multipy again, there was no way it was ever going to be a healthly preg
i was treated with methotraxate, it was not as bad as it sounds (beware when googling it) i had 2 injections in both my thighs, the side effects where minimal (thank god) and a few weeks later, after many more blood tests i finally got a neg,
now it is not great, but i kept in my mind that this was a better option than loosing a tube,
i wish you all the luck in the world tomorrow, any more questions please just ask me ((hug))