Hi Rachel! Welcome.
You've been through a lot. Be kind to yourself. Nourish yourself.
My first piece of advice to you is love yourself. You deserve it. Learn to love your body just as it is. Not for what it looks like but for what it can do. Yep, you can seek to improve your body - but do it from a place a love rather than hate.
I spent my youth hating on my body and looks and I look back now and think "Dang, wish I'd appreciated what I had."
My second piece of advice is to learn to dress to accentuate your positive assets and not to hide the negative. Life is lot more fun that way. It isn't easy and you'll make some mistakes along the way - but it's a skill that will take you a long way in life. Don't cover up, draw the eye to the good!!! I can't give you specific advice because I don't know your body shape, etc.
My 3rd piece of advice is join a team. It worked before, it can work again. If you're in college there must be all kinds of teams you can join. If not, check out community sports. If you are at university, can I give a plug for women's rugby? It's awesome and there are all sorts of body shapes on a team. I have lost over 30 lbs since starting to play rugby and I'm stronger, fitter and faster. And I'm having so much fun.
But even if you dont join a team, find some kind of physical activity that you love.
My final piece of advice is to find a way to center yourself emotionally. This isn't easy. You'll be working on this the rest of your life. Find a way to comfort yourself that isn't food. You gain and lose. Gain and lose. That's what I did, too. I had a terrible relationship with food and look how fat I am now! If I could have developed a normal relationship with food when I was your age I'd be so much healthier and thinner now.
Read up on intuitive eating. You may not be ready for this yet. But if you are it will be a gift. Whatever you do, don't starve yourself.
Lose 25lbs by 15 April (10 Mar)
Get to 100 kg (220) by 1 May (7 Apr)
Be 205 by race day - 14 July
One-derland by 1 Sept