Miscarriage 😭 how long will it take.

I'm 5+1 pragangt my hgc levals have never doubled only gone up by 50% and then over 12 hours dropped one marker. So they have said its either a eptopic pregancy and I will miscarry every doctor I have seen has told me somthing completly different I'm going back tomorrow for more bloods and a scan (even though my levals are too low to see anything ) Iv never had a miscarriage and I'm sceard. Does anybody know how long it will take to happen or when it might start. As awful as it sound if it's going to happen o just want it to the waiting it's killing me. 😭😭 thanks guys X