Hello all i got a few questions too?

I though i was going start my period on june 27th 2010 which was way early for my period to start then i was off the next day. Then I thought I was going start my period on July 12th 2010 I started a light period then i had a light period from the July 12th 2010 to July 18th 2010. Then i start bleeding a little heavy not major then i blood mid size on July 18th & July 20th 2010. Then on July 21st & Today i was back to a light period has anybody done this before. Because i don't know if i am losing to much blood or if i can be preganant even tho i have a period that i know of a werid one tho somebody help me thanks....