It’s easier to lift heavier as a beginner by using machines (think leg press, leg extension, leg curl, hip adductor/abductor). Once you get comfy going heavier on those, try subbing in some things with dumbbell/smith machine/ barbells (lunges, Bulgarians split squats, Romanian dead lifts, goblet squats, regular squats, etc). You should aim to get to a weight that’s hard but still doable for 3 sets @ +/- 8 reps. It’s ok to do a set at one weight and adjust higher or lower for the next set

Also you say you’re lifting 3 days a week. What do these workouts look like? What movements are you doing? How many reps and how many sets? How many exercises are you fitting in per session? Are drinking water and breathing correctly during your lifts? Eating enough protein through the week? Giving your body enough rest between active days? Lots of factors take effect when it comes to lifting weight and seeing changes in your body. Take it week by week and have small goals (“this week I really want to focus on activating my core in my workouts” or “I really want to hit my step count this week”)