Linda, you don't mention how tall you are at 150 lbs. Because you are a vegetarian, you may be eating too many of the wrong type of carbohydrates, i.e., simple carbs that turn to sugar in your system and cause you to keep the weight on. You also may have restricted your caloric intake so much, that your body has gotten used to starvation mode and your metabolism has greatly slowed down. My suggestion would be to cut out some of the "white stuff," bread, rice, potatoes, and go for a little whole grain, low glycemic vegetables, and beans for protein. You should also eat small meals every few hours to keep your metabolism working as it should.
Good luck!
Can you give us an idea of a day's food intake? Even though you're eating "good", it may not be the right kinds of foods or maybe too much, prepared incorrectly, etc.
What about exercise?