Suggest Remedy To Increase The Body Mass

I m not sure what is wrong but I eat on a regular basis and at one time I would eat a lot much more than normal and I m still skinner I haven t put on any weight but I also haven t lost any, I go to the bathroom after I eat but I do my business like every person I don t throw up.ive been asked that question from my parents from going to the bathroom right after I eat. I wanna know do I have a eating disorder or a disease?