Can someone help me with a question about getting pregnant and the pill?

I really don't want to be pregnant now but my boyfriend of a year and I are have sex now. I am around 3 days late on my length. Today is Sunday and I want to start the pill because I don't want to wait another week. I want to start it on a Sunday resembling it's suggested. My question is... if I am pregnant will taking the pill be noxious or will it just hold no effect? Also, what is the reason for teh morning after pill to be taken inside 72 hours...why the 72 hours. Can someone explain that to me? Thanks for all your assistance.
Answers:

Do you think it can consistency depressing to be overweight?

the pill can be taken up till 120 after unprotected sex but has best result inside the 72 hours. I think its 80% significant. The active ingredients in morning-after pills are similar to those in birth control pills, except in highly developed doses. Some morning-after pills contain only one hormone, progestin (Plan B), and others contain two, progestin and estrogen. Progestin prevents the sperm from reaching the egg and keep a fertilized egg from attaching to the wall of the uterus (implantation). Estrogen stops the ovaries from releasing eggs (ovulation) that can be fertilized by sperm.Side effects may include nausea, vomiting, abdominal pain, fatigue and headache.

If you're pregnant you shouldn't nick the birth control pill because it wont do anything to you cause they're only use is to prevent pregnancy. If you're not pregnant you should really start taking the pill and condoms too for more protection. The pill is 99% influential. Here's some info on the pill.

http://www.mayoclinic.com/health/birth-c...

I dont know if it will harm the fetus but I know that they influence you shouldn't take the pill if pregnant.

My privates smell approaching moldy cottage chesse?

If you are 3 days late why not pocket a test and see what it say. If you have be following the instructions and taking the pill everyday.....it is very unlikely you are pregnant.