I know what you are going through, this happened to me too. I was losing alot of weight fast and my doctor told me it would plateau and it did. For two weeks it was so frustrating, exercising and dieting with no weight loss! Aaaagh!
So I wrote about it here and alot people gave me the tips that you read above and it works! Definately change your exercise routine. I now do an hour 5 times a week, but I started at 30 mins. Also, eat a little more and your body wont go into starvation mode and keep losing. But more than anything, dont give up...its a little bump in the road and you are doing so well!
