Hi Ramona - I've been doing a lot of reading about exercise and it sounds like you have hit the dreaded "plateau". Apparently, exercise is a form of stress for our bodies. Because we're so well designed, our bodies adapt to normalize this "stress" factor. So, trainers are advising their clients to alter their exercise program about every 3 weeks so the body doesn't get a chance to completely adapt, since once it adapts, your metabolism slows down again and you plateau. I started back to exercise at 4 weeks post-op with regular walking

and swimming. This week I'm starting stationery cycling and 10 lb arm weights.

I plan to alter my fitness program every 3 weeks and, once the 3-month period is up, start doing Pilates on the Ball (great isometric exercise to firm up the core of the body = abdominal) and dancercise. Also, with summer coming on I can add cycling. I think the key is to keep your body thinking that things are changing and your metabolism needs to stay in higher gear all the time.
Another metabolism-boosting approach is to divide your food into 6 portions ... 3 small meals and 3 healthy snacks, each with some protein (peanut butter is considered a good fat now!). As we age (30+) we tend to lose muscle; dieting can cause you to lose more. Protein is essential to keeping your muscle mass and, as we all know, muscle burns more calories than fat - about 30-50 more per day!
And, studies have shown that women who eat low-fat yogourt or cheese 2-3x a day get the calcium the body needs to tell itself to burn fat more quickly.
You may want to get your hands on a copy of Prevention's
Healthy Woman 2006. It is an excellent research-based guide to health and weight loss.
Good luck and keep us posted! Mary