Late period, also normally irregular, no signs of pregnancy?

I am a seventeen year old girl, and my menstrual cycle has always been irregular with the exception of one or two months being in sync at a time.

My boyfriend and I had sex about four days before it would have been a month since my last period. It was not protected, but we have used the pulling out method for a while and it has never failed, other than making my period a day or so late. It is now technically six days late from that date, but I have always known my cycle to be at least one or two weeks off.

I exhibit no symptoms of pregnancy. No fatigue, no vomiting, no back pain, or anything of that nature.

However, I have a major anxiety problem and have become unbearably paranoid that I may be pregnant, and my boyfriend is quite afraid also, which causes my stress to raise to uncomfortable levels.

What should I do? We are both in a position where telling anyone is out of the question. Please help ease my mind if you can.