This always seems to happen to me. When I first start weight training I'll feel that worn out soreness the next day or 2 which tells me that I got a good workout in. After about a month it stops happening though. This time around I thought maybe my body was just getting used to the exercises that I was doing so I switched up a couple of them. Instead of using the chest press machine, I started using free weights and also doing dumbell flies for example.
That worked for 1 or 2 workouts but then the soreness went away again. I'm already maxed out on the weight I'm able to safely lift and my last set is until failure. Does the missing soreness mean I'm not being challenged enough anymore? If so how else can I change it up? How do I fix this? Thanks everyone for any advice!
P.S. I forgot to add that I'm currently doing 3 sets of 15 reps for each exercise. I do cardio every other day and my weight training is in between. so for example it's cardio-upper body-cardio-lower body-cardio-upper body-cardio-lower body etc....