Hi OP,
I had this too, so far 4 major episodes of bleeding, no warning. Once I was stood in the middle of a supermarket with my OH and suddenly felt like I had wet myself, looked down to find blood streaming down my legs in spite of wearing a night time sanitary pad. OH was stressing about the cream leather in the car getting me to hospital! Lol
Another time I was giving a presentation to over 100 people, again felt like I'd suddenly wet myself but luckily was wearing black and near the end of my talk. Went to bathroom straight away afterwards and I was covered in blood.
Third time was just at home and 4th literally woke me at 3am feeling again like I'd suddenly wet myself, bed was covered in blood like something out of a horror movie!!
Every time I rushed to hospital, got fast tracked through A&E and every single time my two little twins waved back at me as if nothing was going on.
Doctors never found out why I have these bleeds, no haematoma present, too much blood to be cervix so they think I have one placenta with an edge next to the cervix as opposed to a true placenta praevia, but they can't prove it as scans show main bit of both placentas is a short distance from the cervix.
Has spotting in between these bleeds, first one at 11wks, last one was at 17wks. I was just told to drink lots of fluids, no severe exercise gentle slow walks only for short distances and keep my legs elevated above my hips whenever possible to take the pressure off the womb exit.
Now I'm 22 + 2 days, reading in bed whilst I have each twin booting me on either side!! So don't worry OP - my consultant said after 12wks the risks of bleeding causing an actual MC is very small and although they always checked me out just in case, she was never overly concerned. Said although this is not common it is definitely not unheard of and most of the time just suddenly stops as quickly as it started