Help an extremely underweight teenage girl?

Hello everyone. First off, I do not have anorexia nor do I suffer from a thyroid condition. I am 5'0 and a sixty-nine pounds. Yes, I am quite aware that I am severely underweight. I eat mive amounts of food but I my weight remains stagnated, up to a couple of months even. I eat lots of meat, enough pasta for two grown men, plenty of apples, pies, potatoes, etc, in the hopes of gaining weight, to no avail. Here is the deal. I eat three big meals a day, and I am full for 7 hours after I consume any one meal. I was under a nutritionist's care for two years, with very minimal weight gain. (Few pounds.) I used to eat smaller meals and more snacks but that wasn't working for me. I have recently begun binging on ice cream and ice cream pies, my new addiction. I eat anything and everything in sight, as long as I am hungry. If I am stuffed no one or nothing can get me to eat. Is there a reason why I stay full for so long? I always feel bloated, but that is because I am often constipated. I look very skinny, and it pains me to know that even if people don't comment rudely on my weight, they are thinking it. The funny thing is, as gaunt as I am, I am a pretty girl. I'm not trying to be narcissistic. I still am very self conscious. I am 14 years old. If you plan to have a remark like "OMG you are so skinny, that is disgusting" you best leave it unsaid. Thanks.