Thanks for the query.
It takes at least 3 weeks for one to develop nausea and frequent urination which are earliest symptoms of pregnancy. Hence, one cannot feel these symptoms in just 3 days after sex. It takes time for the hormones to act and body changes to happen to feel the symptoms.
Hope this helped.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.