Oh and as for the addiction thing, I didn't think about it before now, but it does seem likely.
My first boyfriend was my first sexual partner, and it was with him and the abuse and all that he inflicted on me, that my ED really started. I was 14/15 and petrified - I lost 3 dress sizes in about 5 months but didn't realise it was ED, I thought it was just a 'diet' (silly, young, naive me).
However, when we broke up, I was no longer scared. Around 2 months after that I became very promiscuous and in the space of 6 months I'd slept with 5 people (although one turned into a long term 'relationship' - despite being far from what a relationship was - and he is the father of my son). I never really realised that during those months I was 'better' - I ate more, I was healthier, I had more energy, but I needed that fix of something which in turn lead me to sex.
I've slept with 8 people - one of which caused my ED, 5 of which were because of my ED, one because I gave up on someone and one being my fiance. Only three of those lasted more than one night/a few times.
It's weird to think about, but does definitely explain it, well, maybe.