i very much doubt your are pregnant,
theres so many other things that can cause your period to be late or not come
like kim said relax and it might come
if not go to a docs and get checked out but pregnancy is not the cause
i went through the same thing where i thought i was prego and used protection and all but still thought i was cause my period was late, my period was late by 12 days than i got it. your okay, you just need to settle down and not stress i know how you feel and its hard but it will make things easyer.
you said you used protection...if it was used correctly..its not likely at all you would be pregnant especially since its been awhile and your not getting a postive hpt and you got your period after then. your still kind of young and sometimes periods are all over the place when a girl is younger. try to relax and dont stress
if they are still coming back negative after amonth, then i seriously doubt you are pregnant. also, stressing the issue can cause your period to be late. it can also cause you to miss a period, even if you aren't sexually active. if you had sex july 1st, and it is now august 11, then you would have gotten a "true" result by now.