Recommend a protein supplement?

huh?? you mean not completing the full amount of reps you set out to do?

if so +1. I have obviously nowhere near CrazyJames experience, but it's worth stating that my above much bragged about weight increase I've just managed never involved anything directly uncomfortable -pushing myself to the breaking point or the like.

No no, I mean maxing out until failure, e.g. hitting a weight you can no longer lift, and then working back from that weight set by set until you reach total failure (can't even lift the barbell) those are negative repa, as you've already reached muscle failure at your max weight and you are then effectively working backwards to zero (barbell only).