WELCOME! And kudos on a first step!
I have found, the best use of this site is to just jump on in. Everyone is super supportive. I have been here for less than 2 weeks and already have gotten more encouragement that I ever dreamed! Every little milestone, be it one pound or 10 has been applauded. That gives me the motivation I need! Join a daily thread for accountability. If you post daily, it makes you accountable to yourself, and others. That helps keep on track, especially when you see everyone else sticking to their guns and you don't want to be odd man out.
As for family, they will support you. Guarantee it. And if they don't, bah to them. It is times like that when sometimes, family isn't everything. But they will support you. I can't imagine a family one who belittled someone for trying to get healthier and happier. Tell them you have decided it is time to get healthy, you want their support, and that you need them to help you stay on track (i.e. don't offer you goodies or waht not until you are in control of your diet.)
The best part of any diet is excercise. if you don't do it already, start. You will gain before you lose, but it will be muscle mass, and you need that to lose.
As for diet plans, different folks, different strokes. It depends who you ask. Some swear to Weigh Watchers. Some swear to Ideal Protein, Medifast, New Lifestyle, or Wonderslim (personally, I am a Wonderslimmer and in 10 days, I have dropped 13.1 pounds.) Some swear to counting calories and carbs. It just depends on what you want to do and what you can handle. Don't join a diet just because someone says it works. Start a diet you know will work for you, taking into concideration your own abilities. What I mean is, don't go on a liquid diet if you hate shakes. Don't go on a veggie diet if you hate veggies. Don't go on the Atkins diet if you hate meat. Find one that will work for you. There is advice galore on here, women and men who have overcome huge obstacles, and a support system out of this world.
Welcome to the forum, and good luck on your endavours!
OH--also--0% body fat is impressively dangerous (abeit deadly.) So, I doubt your boyfriend is really at that range.