Hello Good Evening,
There is nothing possibility of getting pregnant, if you had your regular menstrual cycle after having sex.
Menstrual cycle is the cycle of changes that occurs in the uterus
and ovary for the purpose of sexual reproduction.
It is essential for the production of eggs and for the preparation of the uterus for pregnancy
If egg get fertilized with the sperm then fertilized egg get implanted in the uterus wall after some days, and next menstrual bleeding does not occurred.
It means you have your regular period on time then it means there is nothing like pregnancy.
Amenorrhoea (missed period) is the first and most important sign of the pregnancy, hence you are not pregnant.
Your symptoms are not related to pregnancy, you should consult to your GP, if they remain persist.
Dr. Naresh Jain.