Confused ivf tww bleed

So I'm on my first cycle of <a href="">ivf</a> and in my tww. I had embryo transfer last Monday the 12th. On Sunday I started bleeding very light stringy brown blood then went bright red then stopped over night. Yesterday morning Monday the 19th started bleeding again brown blood so I did a pregnancy test and it was negative. The bleeding continued all day still very little going from brown to red then back to brown. This morning woke up still the same so at lunch time I thought I would test again as I had a feeling of hope so tested at it was bfp so feel over joyed but still lightly bleeding red blood again. So confused am I or aren't I? Has anyone else experienced this type of bleed and still ended up with a healthy pregnancy?