The unprotected sex can make you prone to unwanted pregnancy
. But since you have mentioned that you have your periods that was although not heavy. If it was a period and you have this for 3-4 days and after that it goes off, means that you have a period of less amount and duration. If this is the case than your chances of being pregnant is very negligible. But if it is the case of blood spotting only than you have to make it confirm.
I would suggest you to have a pregnancy test at home to make this confirm, which will relieve you from the anxiety
and uncertainty. Usually the home pregnancy kit will give the result after missing your periods for the pregnancy.
As far the symptoms you are mentioning, they are not the confirm signs of the initial days of pregnancy, but it can be because of some sort of infection also.
Thanks and take care