Hi and thank you so much for this query.
Unprotected sex can lead to a pregnancy
but it does not guarantee that you will fall pregnant. Even unprotected sex during a fertile period does not even guarantees a pregnancy.
The symptoms of pregnancy are so non specific that they can never alone be used to diagnose pregnancy. If you did this test at least 3weeks after your periods, then it means you are not pregnant. These symptoms are often transient and don't always signal a disease. I will suggest that you monitor over a few weeks and see if they continue before seeking any medical attention.
I will like to suggest that you plan on talking with you doctor about the various methods of contraception
and what can be best for you if you should consider using one. Also, unprotected sex in addition to exposing you to becoming pregnancy, it also exposes you to diseases. So please, always consider using protection during sex.
I hope this addresses your query fully. Feel free to return with more questions.
I wish you well.