Awful smell in en suite

[dramapenguin]

It reeks and it has done since Sunday, I've tried drain unblocker, bleach, boiling water down plugs and checking to see shower plug wasn't blocked. There is no window in there so I always leave fan on for a while after a shower and throughout the day I always leave the door open and bedroom window to try and let some air in there. Regardless of all that the smell is rank and I have no idea why? DP is away for work but doesn't know much about plumbing anyway and I know even less. Any ideas what it is and how on earth I can get rid of the awful smell?

Can you work out where exactly it’s coming from? I had this in my en suite and it turned out that my sink needed a new fanny trap (yes, apparently that’s really what they’re called 🤦🏽‍♀️🤣). The smell went so soon as I had a new one fitted.

You need to work out which hole it's coming from!
I've had this twice in two separate bath/shower rooms.
First was the bath - needed a new, deeper trap in the bath.
Second was actually the toilet in the guest shower room - no guests for a year due to Covid, and the toilet water had literally evaporated over time (lovely warm room). Cheap solution - use that loo once every week!

Is it possible any of the outflow pipes are leaking into the wall or floor space, OP?
My local hospital had this in the labour suite - the toilet outflow was leaking into the ceiling void of the floor below. The poor plumber who removed a ceiling tile to investigate was deluged in human waste…