Hello Kerra,
I'm 44 and fighting the battle of the bulge myself.
I agree that you should take some time to monitor your diet. I use fitday.com to do just that. It may take some time to tweak your diet a bit so be patient with yourself.
Body for Life is a great book to start out with.
3 sets of 15 reps is okay. But I found that I did better going heavier and lowering my reps. At this point though I would work on your diet first and then you can revaluate your training.
20-30 minutes on the treadmill is fine. Look into HIIT cardio. There are posts and links here on the board to explain the difference and benefits of HIIT cardio.
And I agree...changes come about slowly. It took my body awhile to adjust to the changes after I quit smoking.
Be patient with yourself.