4-5weeks and spotting for 10days

I am between 4-5weeks pregnant and from 2 days before I got my bfp I have been spotting brown blood with 1 day of a quick pink/red bleed its a light amount but has been happening now for 1.5weeks I had a scan yesterday and nothing can be seen yet besides thickened uterus lining. My hcg has been doubling every 48hours the whole week & my tests have very strong second lines. Has anyone experienced this & what was the outcome? I have been seen several times & told it could go either way.