I'm 135 lbs and trying to lose weight. Help!?

I am 16, 5'6", and 135 pounds. I eat 3 salads a day without any dressing so it's only about 100 calories. I drink only water and milk. I also workout with weights for 30 mins almost everyday. I would workout longer but my ears start ringing and my vision goes black and spotty. I've been doing this for almost a month and have only lost 5 pounds. Can someone PLEASE give me some advice on how to lose weight? I want to weigh 120.