Thanks for posting the query.
As you said, you got your periods after having a safe sex
, it is very unlikely that you are pregnant.
About your growing stomach, it could be related to your gastrointestinal problems like gas collection. Abdomen will not expand in 20 days after conceiving. It takes minimum 3-4 months for the abdomen to increase in size.
Further I would like to know about your last menstrual period and also the date you had sex. Do you have any associated symptoms like constipation
, etc. It will help me to guide you further.
I would suggest you to consult your physician and get yourself examined.
I will be available if you have any follow up queries.
Wish you good health.
Dr. Jyoti Patil.