Breastfeeding + Losing Weight.

Hello! I've done this once before, I was almost 2 years PP. I lost 35lbs in FIVE months! (so sad I got rid of my old name JennBurke987) Then I got pregnant with my third daughter. I'm currently almost 13 months PP - I'm still nursing 3-4 times a day. I use the breastfeeding tool in my foods because that takes off 400 calories. I've been going to the gym religiously - weight training, elliptical, treadmill. Burning AT LEAST 700 calories everytime I go (our gym was just closed for a week for renovations, but they open back up today!) If I go like 5 days a week, and stick to my 1500 calorie diet, I should be losing weight - INSTEAD I'm here struggling and not losing even an ounce. I'm only gaining ounces, like .2 at a time..... HELP!!! What do you suggest??? I need to be back to 148lbs - I'm currently standing at 173.

TIA!!!!