Sneaking a little more weight on the machine

I'm trying to do my weight training on my own one day a week, checking in with my trainer less and less often. He sneaks a little more weight on the machine, and I don't notice it until about 2/3 the way into my reps. I want it to feel easier, not harder, but the way to improvement is built on what he calls "burn" and I'm trying not to call pain. My weight loss is still "maintaining" although I'm less careful of my diet. I'm not ready to try to lose more yet, but I wouldn't mind if it just happened. Ha! There are too many ways to measure exercise -- resistance, repetitions, time, intensity, speed, calories burned, heart rate. Nothing seems to actually correspond with feeling stronger, healthier, more energetic? Is this too subjective? Or maybe it sneaks up on you, too.