Bleeding every week since 12 weeks pregnant.

I had multiple episodes of heavy bleeding. Went A&E 3 times within 2 weeks but baby is fine. Cervix is ok too. Doctor couldn't find the cause of the bleeding. Now I'm 15 weeks pregnant, and still bleeding. Everytime we did scan, we couldn't find any abnormalities. Anyone experience this? I'm so anxious everyday. Bleeding not stopping.