Congratulations on the 50 pounds! That definitely shows you're able to lose weight, and you've gotten into a good rigorous activity pattern. However, if the total time you've started the new plan is two weeks and you've lost two pounds that's pretty good.
That said, there's a few reasons people may not lose weight. First, it sounds like you're not eating enough calories for all the calories that you burn. Did you get the 1,200 from the alli Personal Calculator or did you choose that number yourself? It's important to do the Nutrition and Activity Logs along with the weekly check-in, and follow the calories and fat for your level.
You may not be eating enough fat. If the diet doesn't contain 30% total calories from fat weight loss will be slow. There are two great posts at the top of this message board about why calories and fat are so important for best results with alli. Take a look; it's great information.
I'm not sure how much weight you have to lose, but generally speaking the more weight people have to lose the faster they lose it - at least in the beginning and then it tapers off to a slower, more steady rate.
You may also have an underlying medical issue that is preventing you from losing weight. If you haven't had a complete physical - with labs - in the last 6 months you should definitely check it out.
I hope this helps.
Pat Baird, MA, RD, registered dietitian