So when I started training I felt my muscles extremely hardened immediately after a workout, my abs were like touching a wall and my biceps looked at least 10% bigger (I'm not bragging).
Lately however I get to the point where I feel complete full body exhaustion before I reach the point where I feel the extreme muscle hardening.
I workout using free weights, usually 6 exercises, each exercise in 4 sets of 5 reps. It usually takes about an hour, with my main goal being building strength. I've been doing this 3 times a week for a little over an year and a half now.
My nutrition is standard low carb diet (about 40% protein / 60% fats, I eat cake/sweets max 2 times a week no more than 100g).
So my question is can change my workout or diet somehow to increase my endurance or should I increase weights or is this simply "normal" ?
To answer the comments.
I'm currently doing: pull-ups (with a 9kg dumbbell in my feet), standing curl to Arnold press with 15kg dumbbells, squats with 90kg, lunges with 2x24 kettle bells, renegade rows with 2x25 dumbbells etc. usually exercises including multiple muscle groups.
I can't remember what I started with exactly, but I remember I couldn't to a single pull-up with my body weight only.
I rest a minute and a half between sets or 2 mins max if I'm extremely tired or am feeling slugish, but that rarely happens.
Oh and I weigh 67kg.