I've been having stomach ache for 4 years, will it ever be over?

First of all, sorry for my bad English, it's not my first language. My name is Alison, I'm turning 18 next week and I'm about 101 pounds and 5'8 (46 kilos and 172 cms). I know that I should weigh more because that is disturbingly little for my height. My problems started in march 2011 I noticed that more and more often my stomach would feel heavy in the evening after I eated a bit more for dinner than usually, but I didn't take it too seriously. Then after a few months it started getting worse and worse. I felt nauseous after breakfast and I couldn't eat in school etc. (For the record I used to eat so much..I was never fat or anything but I used to eat cereal in the morning, a sandwich in school then a two-course meal for lunch, something in the afternoon like a croissant then I would eat a regular dinner.) The doctors hasn't found anything and all of them says that I only make it up in my head (my mother says it too) which makes me so mad because why the hell would I skip meals, if I could eat. So in the past 3 and a half years I've been eating less, because whenever I eat normally I feel like there's a watermelon in my stomach and it feels so heavy and full for about 7-8 hours and it's the most discomforting feeling ever. For about the last six months I've tried to only eat when I get hungry which has led me into eating once or twice a day. I never drink fizzy drinks, I don't even eat fast foods anymore (giving them up was really hard), I don't drink milk anymore either (because it makes my stomach want to jump out of my body), I don't know what else I should cut down on. Whenever I'm going out with my friends or having a party I'm not being able to enjoy a slice of pizza or an ice cream or anything and seeing them eat as much as they want always saddens me. I'm so sick of this feeling. I'm going to have colonoscopy in two weeks and I know I shouldn't say this or feel this way but I hope they'll finally tell me what's wrong with me so I can get cured. Is there anyone out there that has the same problems as me? I would be really happy if I could talk about it with someone that finally understands me and doesn't say that it only exists in my head.

I meant to say gastroscopy not colonoscopy, sorry. 

Hey Alison sorry to hear that and my English is not so good I'm Mexican ✌ hopefully they find something in the before the colonoscopy did u have a endoscopy maybe u have some kind of bacteria or infection is not in ur head I hade a bunch of test labs like poop blood and every single and negative have u bump ur head or ur ears ?

heyy alison, I have been having abdominal promblems for over four years also, including chronic abdominal pains that have forced me to cease work temporarily, vomitting regularly, problems eating, being active without pain is also impossible. I get irregular periods, pain during sex and more. I had alot of tests from endoscope to ultrasounds to blood tests and everything came back normal. Was constantly told by medical staff that there was nothing wrong with me and it was all in my head. Until about 5 weeks ago I started seeing a new doctor and he decided to have me go see a Gynacholegist Specialist. Turns out all my problems could be caused by Endometriosis. A simple Laparoscope is all it takes to find out and fix my problems. And apparently 97% of my symptoms are related to signs of Endometriosis. So if they keep telling you nothing is wrong and nothing shows up with any of your other tests, get your doctor to test you for this. A Laparoscope is the only way to tell if you have it but it is really worth it. Good luck i fully understand what you are going through.. xx