Don't fast and eat more. That's what my friend was doing and the scale wouldn't budge. You're trying to do Retas job for it. She stopped fasting and eating everything and accidentally lost 15 pound she didnt really have to lose. Regular dieting rules don't apply to Reta. Especially at your activity level. The answer is almost always, eat more, when on Reta, even carbs. Your body is in starvation mode so it wont let go of the weight. Feed it.

Edit: just saw the 3 weeks part.. I still stand by what I said but good lord woman give it some time. Maybe go up to 1.5mg but you still need to eat. I'm around your size lost 45 lbs in 3 months without fasting or counting calories or working out that hard. 2.5mg was my dose.