has anyone had subchronic hemmorage?

I'm 15 weeks. Went to the hospital due to spotting and they said my placenta was lifted? And I was having a subchronic hemmorage with a threatened miscarriage. 
He didn't explain it alot. Just said i was on bedrest and it could be very damgerous and i would need to be monitered very closely because its dangerous in thw second trimester. Im really scared! This is my second pregnancy. Has anyone has this ?