Hi Jazy..
Take it from someone who knows.. when you first start the contraceptive pill, you should take it for at least a month, have a normal period, and then 'think' about having unprotected sex. To avoid not just pregnancy, but some serious unwanted diseases, you should always have a condom with you.
The symptoms you are going through are normal for some young women who are starting on the pill and sometimes their boobs even grow a bit more, feeling swelled up. Don't forget that your whole system has to get used to the change in hormones. This should not worry you.
The Plan B pill also has a tendency to make you spot, whether you 'conceived' or not, as it's function is to break down the 'bed' so that an egg cannot attach itself.
May I suggest that you make an appointment with your GYN doctor and wait this month, and if possible, the next month out before you have unprotected sex again. Even though, I personally don't think unprotected sex is a good idea.
If you know your b/f very well, and you can 'talk' to each other.. suggest he take as many precautions as both of you need to have joy and fun in growing up without all those complications.
Have a safe and happy youth..

There is something to the saying: "Better safe, than sorry"