Identifying a Foul Odour in House?

I have lived here for 7 months with no smell. Now there is a cloying 'scent' in my house, mostly in the entry hall and upper bathroom. It is not a foul drain smell, sometimes I think it is a urine smell, but it has a sickly sweetness to it. My niece thought it was a plant smell. It's hard to describe. Who would I get in to check it?

By Bernadette