Thanks to all for your help!

I'm sorry you had to go through all of that. Your ex sounds like a manipulative, emotionally abusive piece of shit, and I really hope you don't have to go through something like that again.

I would definitely explain to this friend what you've typed out here. Just say that you aren't as ready for something else with him as you thought you were, and that as much as you don't want to hurt him, you don't want to get further involved in the relationship. Unfortunately, this is totally one of those 'it's not you, it's me' cliches that people hate... but sadly they happen all too often.

Also you have to put yourself first for this one. Suffering from massive anxiety does no one any good -- especially you (as an anxiety sufferer myself, I know the feeling all too well).

First of all, I'm sorry for what you went through. I've been in a relationship like that, with someone manipulative who used me for affection and financial support, then cheated on me and lied about it. In my case, I snapped and broke up with him (but it took a long time and I lost myself for a long while). For a week afterwards he stalked me, until a combination of things I said and him going on dates with someone else put an end to it, but I was genuinely terrified for a while that I was going to end up as a murdered-by-the-ex statistic.

Your ex was probably telling his new woman all kinds of horrible stories about you. My ex certainly told horrible stories about all his exes, one of which at least is an absolutely lovely person (I know, because I'm now friends with her). And my ex lied to me about his previous relationship being over, though it was still ongoing, so I inadvertantly helped him cheat on his then-gf. Basically, his new gf is as much a victim of his manipulation as you were.

The thing that helped me get over it was to realise that my ex is living in a world which has very little similarities to mine. He genuinely thinks he's the poor victim, everyone is always horrible to him, his girlfriends just don't understand him, etc. etc. etc. I can't understand it because there is nothing to understand. His brain works in a way that is so alien to me he might as well be a different species. It still took the best part of two years to move from hurt over anger/hate to pity and then to ambivalence, so you might be chewing this over for a long while. Don't be afraid to ask for help / go to therapy to deal with this - stuff like that can be very traumatic, and PTSD doesn't necessarily require you to have been in a war.

For your question, I would meet in a neutral place, on a day where neither of you need to rush off afterwards, and tell him that you're no longer attracted to him. I'd leave out the fact that you think you never "really" were, because that just sounds like "all of this was a lie". And he must have helped you in the start, made you feel good, etc., otherwise you wouldn't have started going out with him. So even if you weren't interested in him for "the right reasons" (no idea what those would be, btw), you were interested in him for the way he made you feel or the support he gave, so I don't think it's a lie to say you aren't interested in him any longer.

Other than that, standard break-up procedure: be honest but kind, white lies are okay if they minimise the suffering, steer clear of clichés (it's not you, it's me) even if they're true, because it'll make him feel like he's being fobbed off. Give him time to grieve with you there, forgive him if he's rude, but don't stay if you feel the process is becoming detrimental to your mental health. It sounds like he gave you a lot, catching you on the out from such an awful relationship, so if you can, return the kindness in parting with him in a respectful way. If you've been avoiding him, he probably knows what's coming, anyway.

Hope that helps.

Thank to both of you, I wish I didn't have to do it so bluntly but I guess if it's done in a kind way then it could still work out ok for us to go back to being just friends.