it sounds to me like you might be pregnant... remember you dont need alot of sperm to concive... just take a test ..
It is extremely possible you can be pregnant. The "pull out" method is NEVER an accurate form of birth control. You can concieve with the pre-ejaculate that is released in the beginning of sexual intercourse, and this is usually not felt, and can be very potent. The only way to know for sure is to take a pregnancy test. A negative result may not be accurate this early though. If it is negative, retest in a week or two.
The only way to know if you are pregnant or not us a pregnancy test, whether that be a urine sample or a blood sample - your pharmacist or doctor can help you with that. Although some of your symptoms are often pregnancy related, you may be over thinking things and therefore 'tricking' your body into acting like it is pregnant (if that makes sense). Wait and see if you do get your period before you stress out too much! And with any concerns, big or small, make sure you see your local doctor. They will be able to reassure you. Good luck! :)