E.,
It took me a few years to figure out why I could no longer lose weight the way I used to be able to before my daughters were born. You are on the right track with working out. I'm no dietician, but I will share what finally worked for me - I lost 30 lbs. in 4 months and did not deprive myself of food.
The first thing I was doing wrong was not eating enough. My body went into starvation mode, making it impossible to lose weight. I started working out, too, and although I gained some muscle, I still could not lose the weight and I was ravenous all the time - then when I started eating, I would overeat the wrong kinds of foods.
Miraculously, the weight started peeling off when I ate a high fiber, high protein diet, with lots of fruits and vegetables. Basically, I avoid sugar as much as possible and rarely eat traditional desserts. Now, an apple or grapes or something like that serves as my dessert most of the time if I even feel that I need one. I eat a small amount of protein at each meal, along with something that has a lot of fiber in it - whole grain, fruits or raw/steamed veggies. I also drink lots and lots of water throughout the day.
The funny thing is, I no longer feel deprived, and I am eating PLENTY of good food. Sometimes I have to make myself eat now because I realize that three or four hours have gone by and I haven't eaten - yet I'm not hungry the way I used to be.
I believe that a lot of stubborn weight loss has to do with your blood sugar levels, too. If they are balanced, you will not be hungry. You can balance them by not eating processed, refined carbs (in other words STAY AWAY from white flour, high fructose corn syrup, sugary drinks, and refined cakes, cookies and candy). If you fill up on the protein, fruits, vegetables and fiber, you will stay satisfied. I also take a supplement called glucommanan (available at many health-food stores). It lowers blood sugar levels and cholesterol by bloating up in your intestine and pulling out much of the bad fats and other junk in your colon - but it does not give you diarrhea. One other thing - make sure you are eating plenty of good fats: these are olive oil, fish oil supplements, flaxseed oil, and even extra virgin coconut oil (it is a very healthy saturated fat that can be used in cooking).
I am sharing what has worked for me and changed my life. I went from a size 12/14 to size 6/8. I never thought I would see the day when I could wear my pre-pregnancy clothes. You can do it, too! You might have to tweak my magic formula to meet your unique needs.
I also take a high quality multi-vitamin supplement. I have loads of energy, I sleep better and can deal with life's stresses so much better than before.
Kudos for working out - I used to work out like a fiend at the gym and can no longer do that because of my current schedule, but I take walks with the kids every night and lift some dumbbells at home, along with doing push-ups, crunches and other floor exercises. Because I've changed my way of eating, I don't have to work out nearly as hard and I have seen fantastic results.
I thank the book "Ultrametabolism" for getting me back on track, and giving me very valuable information.
I know you will get back to where you want to be!
Blessings