I am two weeks late for my perioid I have my mirena iud removed on 08/20/13 and had unprotected sex on 08/20/13 & 08/21/13 I still haven't started. I had a very small amount of brownish discharge yesterday but nothing else. Could I be pregnant or what is going on?

I am two weeks late for my period I had my mirena iud removed 08/20/13 then had unprotected sex 08/20/13 & 08/21/13. I had a very small amount of brown discharge yesterday but nothing else. Am I pregnant? Is it too early to tell?