my last period was may 19th and it lasted about 4 days. i was expecting my next one to be the 17th and i experienced a reddish-brown flow for about a day and a half. i wore reguar size tampons, but barely filled two of them. now, three days later, nothing has happened. was that my period? is there a possiblilty that i am pregnant and experiencing spotting? the only time i had intercourse was july 5th and my partner and i used the rythm method ("safe days") and withdrawl. Help!

Optional Information:
Female , Age: 18