I started my period on July 15th and it ended on the 20th. After that I've been trying to get pregnant.. and today (July 29th) I noticed that I'm bleeding, but it's light and I'm not cramping.. So is it my period again? Or what?

Implantation bleeding does occur in some women, but its rare. Some women bleed lightly in the middle of their cycle, when the egg is released from the ovary (also known as ovulation).

But, the best way to be sure is to wait and see if you miss your next period. If so, its time to tak an HPT. :)