I'm A Girl With An Endomorphic Body, How Can I Lose Weight?

I'm having the worst time losing weight. I could lose 5 pounds in a couple of weeks but if I so much as look at a slice of pizza, it'll all be piled back on in one day. I go to the gym, but I feel like my body is intent on being 178lbs (I'm 5'3 by the way.). I changed my diet to low carb, high protein being mostly chicken and fish, but what else can I do? I'm really frustated. I did 45 minutes of cardio yesterday and weighted myself after and the scale said I put on 3 pounds. This isn't making any sense anymore.
I'm A Girl With An Endomorphic Body, How Can I Lose Weight?
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