You may not be pregnant, I'd wait at least a wk then go to your doctor and tell them your late and get a test done.
I was 3 weeks late once it just wouldn't come I'd been to the doctor twice and she said I wasn't pregnant and the day after she got tests organized to make sure everything was ok I got it.
If you know it may happen again go on the pill, its better to be safer then sorry. But Honestly you should use condoms until you've been with your partner for a long time and you both get medically checked out. You never know what you can catch.
I know every1 thinks it'll never happen to me but the odds aren't in your favor.
It never ceases to amaze me that in this enlightened culture people still have sex with someone they're not married to and don't use a condom! Yes you could be pregnant, and yes it could just be hormonal changes. USE A CONDOM! Or better yet, wait until you're married and actually enjoy sex in secure loving environment.
The 1st symptoms of pregnancy appear after your first missed period. Either you are late because you have been stressing out or you are pregnant. So yes my dear instead of waiting go get a pregnancy test from the store.
Your boobs being sore could mean that your period is coming & so could the fatigue. I would wait up to a week and just somehow get a preg. test to be safe. I've been a week late for my period before. so it's really a 50/50 thing, good luck!