Hi Chris, basic rule of thumb: the smaller the room the more it needs absorption. You have the side walls close to your ears and consequently early reflections creating smear, congestion and obscuring detail. Looking at the photo you provided I notice a radiator on the left which will cause problems. I also see some room treatment but the damage from the strong early reflections is your biggest concern.
As an experiment temporarily try some absorption like a couple of mattresses or duvet or similar at the first reflection points on both side walls. Use lots initially to get an idea, which if you like can then be reduced in stages till you find your room having less effect on the music. If you remove the room's huge influence then you get to hear the studio or music venue .. the target.
I have posted before on measuring the room so I won't repeat all that but it's the way to go and removes any guesswork. The science works.