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The mass which you have been feeling requires a physical examination to comment regarding its cause as the size,location,and symptoms associated are quite important in this case.But it does not seem to be related to having intercourse.If you suspect to be pregnant then the first symptom would be missed periods.
It can be due to various reasons as hernia,lump,infection,tumour etc.Kindly visit a Physician for evaluation so that the exact cause can be ruled out and then treated accordingly.
Take care