I have had a smell in my bathroom for 4 weeks, it seems to be coming from behind the sink. It is getting on my throat. I have had the environmental health people out & a plumber but no answers.

I have had a smell in my bathroom for 4 weeks, it seems to be coming from behind the sink. It is getting on my throat. I have had the enviromental health people out & a plumber but no answers. I had a flood in the yard a month ago is this anything to do with it.