Pregnancy test line got fainter....

Hi all, my husband and I have been ttc for 8 months, and finally got our bfp 2 days ago. But this morning I thought I would test again (you know, cos I still can't believe it!!!) And the line was fainter than 2 days ago..... this happened to a friend of mine and it ended in miscarriage.... I was wondering if anyone else had experience with this happening and it being ok? Or if its a pretty clear bad sign....? Thanks everyone