I'm having difficulties

So I'm 18, 5"1, and 98lbs. Is that healthy? Everyone that I know tells me it's wrong and that I need to gain weight but my problem is that no matter how much I eat I can't get above 100lbs. My mom says it's because I don't drink milk or eat bread? Could that be the problem? I know most models stay skinny because they "don't eat bread", which honestly I don't believe, yet it does raise a few concerns because what if I did start drinking disgusting milk and eating bread that has a horrible taste. Oh by he way if you haven't noticed bread and milk are not my friend.