Vomiting problem, Dr assumed it was to lose weight...

im 15 and can't stop vomiting after almost every meal I've eaten. its been about 2 years now. I've tried several medicines for acid reflux, which didn't help at all. then i started seeing a gastroenterologist for a few months he couldn't find out what was wrong either. so i had a colonoscopy and endoscopy a little over a year ago. everything seemed normal. so i stopped going to him. but i still vomit constantly which makes it difficult to go eat out with friends, even though i can swallow it which is gross but it makes my stomach hurt. my doctor thought it might be certain types of food so he put me on a special diet but i still vomited it didn't matter what i ate. it was much more of a concern when i still went to my gastro doctor because my weight would go down every time i saw him. i went from about 141 pounds to 121 pounds and I'm 5'7. its still in the normal weight range though for my height and age. but my weight hasn't decreased recently. but i didn't really like my gastro doctor and stopped seeing him because he just assumed that i did it on purpose in order to lose weight, if i did why would i be there seeking help..? so then my parents agreed with him and the topic of my vomiting at home is just kind of normal now...they don't really care anymore i guess but i don't at times either its just become so natural now. i really don't know what to do since my doctors can't figure out anything that could be wrong with me so thats why I'm here writing this post, sorry its so long. oh and the details about my vomit is that i usually vomit 10-15 mins after i eat. i have a weird burp sometimes and it comes out. not a whole lot of vomit. maybe 5-7 times of smaller portions of it at a time. i can vomit smoothies and drinks like that too. I'm just looking for suggestions.