Hi,
If you have mentioned the day of menstrual cycle when you had intercourse and used any
contraception or not, more accurate answer is possible. Anyhow according to your description, I am assuming that you had intercourse during the first week of menstrual cycle.
Usually in case of regular 28 to 30 days menstrual periods, ovulation can occur between 13 to 18th day. According to this the possibility of
pregnancy is less in your case. If you are having irregular cycles especially with short length, we cannot completely rule out the possibility of pregnancy.
Menstrual cycles between 21 to 35 days can be considered as normal. So, you may be having early menstrual period with dysmenorrhea.
Implantation bleeding usually may not be as heavy as regular menstrual flow. So, please observe your symptoms, if the flow is like regular menstrual flow and pain subsides gradually you can take it as menstrual flow.
If the flow is minimal and pain increases gradually, better to consult Gynecologist once and get examined to find out the possible cause of the problem and treatment can be taken accordingly.
Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Sree Gouri S. R., OBGYN