Confused

I spoke to my boyfriend of a year, Jack, about everything properly for the first time today.
He obviously knew what was going on, he came with me to the doctors appointment I was forced to go to by the nurses at the hospital who threatened to have me admitted against my will if I didn't go, and we've talked about it before. But we've never properly spoke about it in so much detail before.

I started right from the very beginning- I was just a 15 year old self conscious kid who thought she was fat and had mummy issues, who one day turned to comfort eating.
I ate a lot that day, I remember every biscuit, every piece of chocolate, every bite of every cheese sandwich. I knew I was being stupid, but something clicked in my head halfway through that if it went in, it could come out, so I carried on until I actually had a weird excitement about finishing and giving purging a go.
It wasn't as easy as I thought; it hurt, it came out my nose, I stunk.
It wasn't bad enough to put me off though, I just vowed to get better at it.
I remember googling it and coming across a 'pro-ana' website. I had absolutely no idea what it meant, I had never known anyone with any sort of eating disorder and I guess I was too naive to think what I found wasn't normal. Girls giving each other tips on how to purge, how to not eat, how to get away with it. 
My fifteen year old self thought she had just hit the jackpot and immediately thrived to be like the girls posting on the site, they were so strong, they had the self control to stop themselves from eating and more importantly, they were thin.
Soon enough I promised the girls on the website that I wouldn't binge anymore, I would simply purge any meal or snack I had to eat. They assured me this would be better as it would eliminate unnecessary calories I would have been getting before. 
I made friends with one girl, Hannah, who I am still friends with now, that was a similar build to me. We would come up with diet plans, sticking to 200 calories some days, 600 the next, and eventually fasting, weighing ourselves incessantly and comparing our results. It would kill me if her weight was less than mine, and although we sugar coated it as 'helping each other', we were always competing.
I'm not stupid, I'm not passing the blame of my 'problem' to them, it was completely my fault and if I hadn't had the encouragement from them I would have learnt these things myself anyway, but looking back now I was catapulted into a world of unhealthy competitions and guided towards a world of starvation and obsession.
Eventually I was testing myself, seeing how long I could last without eating before my excuses ran out.
"I've already eaten"
"I feel sick"
"I'm doing my homework I'll have it later"
"Can I eat it upstairs?"
The longest I can remember fasting for was 8 days, after that my mum was away and my stepdad thought he'd rent a film and made fajitas to eat while watching it. My conscience wouldn't let me tell him to watch it himself.

Jack's reaction to all this was "wasn't it hard not to eat?"
Not at all. At first it was a struggle, but eventually the feeling of being empty, and knowing that you were doing it, you were winning, was what I imagine a druggies 'high' to feel like.
It eventually became more difficult to get out of meals, and that's when my trusty purging returned.
I'd have to hide containers of sick around my room and wait until the coast was clear one night before getting rid of them all.

Sooner or later I decided enough was enough, I had proved to myself I was strong, I could do it, so now I could stop. And I did get better for a while, until I went for a final bridesmaid dress fitting for my dads wedding and they couldn't do the zip up. I have never felt so worthless and disgusting as I did that day.

I honestly didn't think I had a problem.
I wasn't like all those other girls online, they were so thin and strong, I was fat and weak.
Saying it all out loud to Jack today, and even typing it now makes me realise just how unhealthy it was, maybe I did have a problem.
Maybe I still do, I don't know.

It's been three days since I last made myself sick.
I thought it would be easy, I controlled it not the other way around, but today I had to fight the urge so hard I was in tears and now I'm not so sure.
Jack says I have an unrealistic image of myself and that I'm beautiful. This is all I have ever wanted to hear so why is it still not enough? What am I fighting for?
I spoke to Hannah today too, she told me to lie to the eating disorder people and that since I'm 20 there is nothing they can do, I need to carry on with this and I can't give up.
I really don't want her to beat me, if I quit the game then I have lost. But if I don't quit the game I have still lost, I will lose everything else, including Jack.
I didn't think things would be this hard.