Eating 200 calories a day! HELP!?

okay well i dont think my questions is as urgent as the title - just an attention grabber. k well im a 13 year old girl and i eat about 1800-2000 calories a day then i burn it off because im a competitive swimmer, literally. so on average, i probably eat 200-300 calories a day. is this noraml? im also a little.. chubby i guess. im no fat i just had to take a 4 month break from swimming due to a surgery. my second question is - how many pounds will i loose if i swim and eat like this 4-5 times a week? i want to loose weight but healthily.. i dont think thats a word:) please answer! THANK YOU!