If you haven't had sex, you are most likely not pregnant. Stress can cause all of these symptoms, along with poor diet. If you don't start your period for more than a month, make an appointment with your doctor to be looked at. You might have a hormonal imbalance.
how would semen get there?
you cant get pregnant without having sex, unless semen gets in your vagina. i would take a test just for saftey :). sometimes stuff like that happens cause its just your body working and such. trust me i went to the doctor for what your asking. and with little women abdominal pain is very common and so is messed periods. especially if you have sex. and breast tenderness could be your breast growing ;). just go to your doctor in case and tell him/or her your problems. but take a test first and if it says negative then go to the doctor. if it says positibe you know what your problom is.
have a good day :)
SJ<3