How to get rid of the last few pounds?

Hi I need help with my weight loss plan...

As of right now I am 16, 5'8" and 125lbs. I know that the lowest I should technically weigh is abut 122, but I still have a few stubborn pounds I want to get rid of and so I'm aiming for about 120 or a little under and then I'm gonna build up muscle to add weight and tone up. 

I've been dieting for about 5 weeks and in all I'd say I've lost 15-20 pounds. It started off fast and then when it slowed I started to take measures to keep it consistent, such as lowering my caloric intake and raising my exercise level. However, I've noticed that it's virtually stopped and my weight is staying about the same now. I'm eating about 1000 calories a day and I do a swim workout almost every morning and 40-60 minutes of running every day or every other day.

What can I do to lose these last few pounds? Should I temporarily eat less or should I start eating more? Should I exercise more or do different exercises? 

I don't know which chart you are going by but 125 is the lowest us 5'8" small framed girls should be and ideal is 130-134. I mean your are trying for BMI 18.5 exactly? that is too aggressive I mean 0.1 from underweight is not really an argument for "I know I am allowed to lose about 3lbs". I don't mean to be harsh but I cannot tip toe around this red flag.

1000 cals is starvation for a adult and horribly starving for a teen. Your 16 even if you grown 1/2 an inch to an inch more your under weight. Stop before you hurt yourself, stick to fitness goals and stop letting numbers give you a complex or an ED. But really please stop before you hurt yourself (I cannot emphasize this enough) and before a mod comes here and locks the post or gives a warning.