Since I first got my period (13 y/o) I used to have very irregular cycles. I went to my doctor and for three months I started taking birth control pills, and after those three months I had cycles very regular. That was when I was 18. Now a few months ago I took the postday pill and waited until I got my period, one week later I got my period and started again with birth control pills just for one month because they produced me very bad headaches. So I got my period on June 8th. And until then I haven't got my period (no sex at all in June, in July 8th I had a relation) we've always protected oueselves. But now its already August 14 and I hadn't have my period yet! What could be happening?. I already took a pregnancy test. (NEGATIVE)

If the "post day" pill is the morning after pill, it can stop your period for one or two months, plus other side effects.

Have you dismissed the headaches with doctor, have you discussed other birth control pills.

Not sure what other protection, but condoms have a 3 to 18 percent failure rate.
Perhaps wait till you are due next month and if still no period, go to the doctor.