What Causes Light Spotting And Bleeding?

Me and my fiance have been trying to concieve. A few days ago I had some very light spotting which we believe to be some implantation bleeding and then stopped, but as of today Jan 10, 2011 it seems to be a little more but still light in color. In the past it has been very hard to conceieve. I would like to know what should I do or is this normal, because I have felt that mother's intuition and had some signs of pregnancy. I have taken two home pregnancy test around the end of December and both were negative