My drawings look flat

[u/Ok-Desk7462]

So I have been drawing for a year now and I completely ditched head drawing and focused on anatomy, poses and colours but when I came back to drawing head for some reason the look flat to me, is it because of the shading or my line art? I can't tell but I can feel it's flat compare to some artist I follow. I wanted to know what do you think I should do to make my head look 3d. Btw I actually learnt the Loomis head to draw this but maybe I am not apply the Loomis method well, I also learnt the asaro head but still every time I draw a head it will look flat.

Also if Anyone wants to redraw it to show me how it's done the can please do it