I am so thin but i eat a lot. what does it mean to my health?

The first thing: someone would want to check is your thyroid...an overactive thyroid could cause this (though you would probably have other symptoms, too, like palpitations, tremors, etc). Some people are just constitutionally thin; if you are actually underweight (BMI <16-18), review carefully with Doc for other conditions/eating problem. You may need to be on a prescribed weight gaining regimen with supplements