Feels like something is floating in the belly after sex

Hi,

I am 29 years old & been married for 3 years now, we have always used condoms as protection but now we are trying for baby, so now after sex I feel like something is floating around my belly/ I don’t know may be gas & feel a very light pain for sometime (like we have during periods) .. is that common if you have sex without protection? or do I need to go to the doctor.