Getting pregnant while on the birth control pill?

I have been on the pill for several months. Usually when it is time to take the pills without hormones (the week you start your period), it takes a couple days for my period to actually start. I recently had sex without any other forms of protection, and now it has been three days since I was supposed to start my period. Isn't your period supposed to be more regulated when you have been on the pill for awhile? Any thoughts? Should I get a pregnancy test? How late can my period be before I should start wondering?

millions of women have gotten pregnant while on the pill.
take a pregnancy test.

see your Dr you may be pregnant
If in doubt, use a pregnancy test kit. Don't worry. Pops
My thoughts
Ok first of all, take a pregnacy test. If you are pregnant, then you could sue the company for a lot of money (i think)
But im not shure thats possible
If you are having doubts then take the test. There still is that chance you can get pregnate while on the pill. It happened to my sisters friend 3 times. Not to scare you, but just to let you know. =)
If you have been taking the pill exactly as you are supposed to you shouldn't be able to get pregnant. Make a doctor's appointment or go to a womens clinic and get yourself some answers, but the pill taken properly usually works. Some people take the pill to regulate, you are right.