trying not to stress over it

We have been faithfuly trying to get pregnant for sometime now. I have been experiencing odd periods lately, well what I think are periods. I got my period on the 15th of june it was heavy at first and by the end of the day i was only spotting. the next day it was gone. My period always lasts 4 days. I was not supposed to get it again until the 21st of july, I got it today the 17th and it is light. it looks either dark and old or light pink. I don't feel like I would when I have my period. Also for the last few weeks I have had symptoms that make me think I maybe pregnant. We don't want to get our hopes up yet though.I have a 10 year old daughter and I never could get a positive pregnancy reading on a home test, I had to have a blood test. I took two test over the past few weeks and both were neg so I don't know what to think, is this just my period or could we finally be pregnant?