Does Delay In Periods Indicate Pregnancy?

i had my merina for 2 1/2 years and never had a period when i got it out on march 24th 2010 i got my first period the 27th of march lasted 5 days normal then now it is may 14th and still have not gotten a period since i have taking home pregnanct tests they say negitive but i feel pregnant so couldi be or is it commen for me to not get a period. oh and alos never had irregular periods before the iud