Need help gaining weight for an anorexic 17 year old!!

Hi.. I'm new to this site but really need some help. I'm 17 and have lost over 40 pounds pretty quickly from not eating. I weigh currently 102 pounds and I'm 5'2. I've gone from eating nothing at all to 500 cal, 800 cal, and now range from 1000 to 1200 per day. I'm terrified of fatty foods, carbs, high calories, desserts, soda, fast food, etc. I eat only fruits and veggies and occasionly some proteins. I weigh myself more than 4 times a day, walk, and bike daily. I barely drink water cause im scared it makes me gain weight. My boyfriend has pushed me the past few days and ive had some ice cream for the first time in months. But i havent gained any weight and its been 3 months since my last period. Im scared of how i look cause my bones show bad but im scared to eat anything. I just had dinner and my stomach hurt from eating a little more than usual. Can anyone please give me advice on how to gain weight and overcome this problem? Thanks for helpinggg!

Please see a doctor, first and foremost.  It is good to have solid, reputable medical advice on this journey AND accountability.  A doctor will keep track of your progress for you.

Then, get rid of your scale.  Burn it.  Run it over with your car.  Drop it outside the window.  Whatever you have to do.

Drinking water will not make you gain weight. You know that.

You need water. You need to gain weight.  When you stop getting your period, it is your body telling you something is wrong.  You only have one body.  It doesn't know what being "fat" or "ugly" is.  All it knows is that it is not getting enough nutrition to perform regular, healthy functions like menstruating.  Our lives are so short and so precious.  You are young and need to be enjoying this time.  Please, please treat your body well.

Obviously you know you have a problem here and you know what needs to be done.  You have to eat (gasp!).  Food is sustenance.  Food is what brings people together.  There is no reason to deprive yourself.  A 2500calorie(or more)diet, without exercise, is reccomended for recovery.  Best of luck.