/ic/ - Artwork/Critique

Please. My Anatomy (specifically male anatomy) Is really garbage and I'm starting to notice a trend of this.
Can someone Please Crit/Redline/Destroy me so I stop getting this so wrong. :C

His chest is sunken, I don't know how to define abs and also express taut skin stretching/squishing across the surface of the body, my lighting is garbage, but I've resketched it several times to try to re-establish the rib cage and pectorals while examining anatomy reference but it always looks just as garbage.
Just... help... please.