So my first ectopic I had a really heavy bleeding just a couple of days after when my period was expected. I had extremely faint positives at the time, dismissed as a evap. Two weeks later I had darker tests. Much darker. But, it self resolved, which means the body re-absorbed the pregnancy tissue.
The bleeding is from the uterus - it sheds the lining at the correct period due time. This is because the HCG is too low to stop the uterus lining shredding. Because there's no pregnancy in the uterus, right?
But there is a pregnancy - in the tube. So after the bleeding and the lining shedding - it makes no difference. It hasn't shifted the pregnancy, which remains growing, usually slowly, in the tube.
The pregnancy can only get so large in the tube, it's not designed to grow there. Often, your body will recognise this before it gets too big, and the pregnancy will stop growing, and the cells will be reabsorbed.
Sometimes, the body will not recognise this in time. The pregnancy keeps growing and the tube bursts - a ruptured ectopic. This happened in my second ectopic pregnancy.
Ruptured technically can happen at any point, but the lower the HCG the lower the risk. If HCG is low, and declining, it's usually safe to moniter and see if your body can 'self manage' the situation. If HCG continues to rise, you will likely be given drugs to try to stop the pregnancy continuing, which have around 70% chance of working (the drugs didn't work for me, hence the rupture and surgery).
I'm sorry if that all sounds clinical. I get the heartbreak I really do, but I didn't understand anything during my first one, I didn't get why I was bleeding but still pregnant etc etc. So I hope that helps you understand.
Against my will I've become an ectopic expert.