Stuck "guessing" my low end: How to optimize Yamaha HS5s in a terrible, tiny room?

I own two yamaha hs5s, and hd280 pro from sennheiser. and some budget behringer uphoria audio interface or whatever the model's name was.

The thing is my room is in a weird shape. I can provide an image of my room if that would be better, I think it doesnt matter since I cannot invest in panels - my room at the moment is just too small for a correct monitor placement.

Speaking of - my monitors have to be on my desk. They are like a meter apart, but around 80cm to my face. 20cm from the concrete wall behind them. I just cant move my setup to a better position. Maybe I can increase the distance from the wall but I'd still sit the same distance from the monitors.

Whenever I make my own music and mix/master it, I always have to GUESS. It's so frustrating. Some frequencies are juat not audible, some are boosted, it's a mess on monitors. I usually use hd280 pros, which also have some frequency response issues.

I tried using impulse response for the headphones, but I'm not sure if I'm using it correctly.

Is there anything that I can do to get slightly better audio coming from my daw? I wont get studio quality sound here but I'd at least want to hear low end coming from my monitors lol. I cant hear shit below 100hz sitting this close. I need to stand up and go to the opposite wall to hear the sub on my monitors.

Maybe I could get monitor stands and put the monitors behind me? I dont know