Weight-loss help!

I'm 19 almost 20, 5 foot nothing and weight 150 . I can only do core workouts do to a leg injury I got years ago. I watch what I eat and only drink water. I have cut all sugary drinks and foods from my diet and eat extremely healthy for a 19 year old. Recently a regular customer at work called me fat. Then she asked how much weight I have gained. I have been between 145-152 lbs for over a year. With all that being said I need to loose weight but have a hard time dropping it. No matter what I do. Any ideas?

UPDATE: I have had my leg injury looked at and have had surgery. I tore all the ligaments in my knee. The doctors wanted to do a full knee replacement but will not do one until I am much older because they only last 6-10 years. So they did what they called a "patch work surgery which had a 75% chance of working,20% chance of not making anything better and a 5% chance of making things worse. I went ahead and got the surgery and ended up being in the 5% category.