I have been trying to lose weight for some time now, but it has been an extremely long process and I still need to lose around 15 lbs. I eat a fairly descent diet (I'm in weight watchers), and I LOVE to exercise. I exercise 5-6 days a week for about 45 min, but I only do cardio (walking or jogging). I have always been a little more on the muscle side of the scale, therefore I'm leary of weight lifting. Everywhere I look, it says to lose weight you need to also do weight lifting/strength training. Does anyone have any suggestions of how I can change my routine to include some strength training without making my muscles any bigger? I actually need to lean down the muscle that I have. I've tried to not use some muscles to make them shrink, but that hasn't really worked and in reality that's not the healthy thing to do. I'm really confused about what type of exercise I really need to be doing in order to lose weight and slim down my muscles that I already have. Any help will be greatly appreciated!!!

You can't really slim down muscle unless you are on a serious calorie deficit. The body would have to be allowed to cannibalize the extra muscle tissue, and it isn't especially healthy. What you can do is either Pilates or Yoga workouts wich tend to tone without adding bulk, or try resistance bands which can help you tone without really giving you enough resistance to get any bulk. Just doing strength training 2 or 3 times a week should be plenty.
You might also kick up your cardio workouts. Intensity is very important for weight loss. If you can jog or run more than walking, maybe doing intervals of sprints and occasionally going for a full 60 minutes. Are you going to a gym or just outside?