Ok lemme see if I understand this correctly 2 weeks ago (14 days) your period started...One week (7 days)after your period started you started taking the pill and four days after that you had unprotected sex. That would put you at 11cd...Depending on the length of your cycles and when you ovulate, you may very well be pregnant but it would definately not have implanted yet .....However I surely doubt that what you are feeling now are pregnancy symptoms. Because the egg will need time to implant, produce hormones etc.
Wait another two weeks then test........It should show up on a pregnancy test by then. It may very well be the bc causing all of this, but youneed to take a test just be sure.
For future reference use protection at all times when you first start the pill until it is able to get into your system.....I think its 2 weeks if you start taking them during your period and like 1 month if you start taking the in the middle of your cycle (don't quote me on this....Its been a while since I have been on bcs) read the instructions or talk to your doctor for the actual time frame.