A couple thoughts:
* I do think that you should do higher weights, and smaller numbers of reps, if your goal is to build and strengthen your muscles. I aim for the weight that I can do 6-8 reps/set, for 2 sets. When I find I can do 10 reps easily, it's time to up the weight.
* If you are lifting that way, don't do it every day - let your muscles heal and repair for a day in between lifting workouts. That's what allows them to build. Some people do lower body lifting one day, upper body lifting the next day, repeat. I do a full-body lifting workout every other day. I do a shorter cardio workout on lifting days - really just a warmup, 15 minutes or so - and a longer more focused cardio workout on non-lifting days.
* Don't be limited to your machines - add squats, lunges, and lateral lunges to your workout. These are the best exercise for your legs, butt, and core. They are great for building functional strength and balance too. You might be surprised at how difficult they are to do, especially the lunges, if you have mostly been lifting on machines. For your core and your arms, you can add pushups and tricep dips (on a chair or bench) - also, surprisingly hard to do. I always thought of myself as strong and did a lot of machine lifting, but it took me a long, long time to be able to do real pushups.