My question is, how come I haven’t been getting sore? I’ve been lifting heavier, getting my protein in, but the last few weeks I only feel sore or tender sometimes. Makes me wonder if I’m not working hard enough, but it feels like I am when I’m in the gym!

Soreness is absolutely NOT the measure of how hard you’ve worked!

The underlying biology of delayed onset muscle soreness, which typically hits 12-18 hours after exercise and is often called “DOMS” by lifters) is not very well understood, but we do know it’s the result of microscopic muscle damage (which is how we get muscles to grow) and that a few specific scenarios tend to cause it.