Hi J.,
I've been an athlete all of my life (competitive figure skating for 16 years, complemented with dance, cross-training, etc. and I continued the pursuit of physical exercise in my adult life with Triathlon). I had 2 kids and some pretty severe feet injuries over the last 8 years, and had some issues with hitting plateau after plateau where it seemed like the harder I pushed, the less things changed. It took a registered dietitian and consistent food journaling, coupled with a radical change to my cardio workouts in order to jump-start my metabolism again.
This doesn't have to be super-expensive. It sounds like you belong to a local health club, so talk to their Personal Training department and schedule a consultation. Take a print-out of your Calorie counter journal with you. Also, if you'd rather not spend the $$ on that, just look at your gym's group fitness schedule and become a cardio-junkie (5x a week of Cardio). Weight training classes are great, and necessary - keep doing them, but nothing gets you going like cardio! Get a heart-rate monitor and take a Fitness test to see where your heart rate training zones are (everyone is way-different). Burning the maximum calories will happen in Zone 3 (under your anaerobic threshold). I love step classes, but they hurt my feet injuries, so I stick to Cycle classes mostly, and typically burn about 600 calories each class.
Also, increasing your cardio work, means you'll need to adjust your diet accordingly. A body needs complex carbs for fuel, so don't skimp on them!!!! Eat a bowl of oatmeal, a whole wheat English muffin with Peanut butter, etc. about 1 hour before your cardio work. Then, re-fuel with a carb/protein mix within 45 minutes after. (I like fruit and yogurt smoothies with protein powder, or fruit and cottage cheese.) I eat an 1800 calorie/day diet most days in the off-season and 2200 calorie/day diet during Tri training season because I burn more like 1000 calories in those workouts. Make sure you take your multi-vitamin.
I'm not a Personal Trainer, just an avid athlete who has learned through trial and error how to change my body during difficult times. Feel free to message me if you have questions.
C.