Morning everyone, thanks for all your advice, I do feel a lot more empowered!
However, I still don't know what to do, I know I can find someone else etc who will make me happy, but I still love him so much.
This is what happened.....
I looked at his phone bill and saw he'd been texting a number I didn't recognise, so in a moment of madness (but glad I did) I text the number, she called be back and said she'd met him on plenty of fish etc and they'd been on a couple of dates.
Ok - so, bye bye to him, however - even though I know she'd have no reason to lie to me, we (me and ex) ring each other loads every evening and he is always at home etc, so I honestly don't know when he'd have fitted it in, especially as she said she'd last been with him on Wednesday, when I know for a fact he was at home as it was the day I came out of hospital and I had to tell him not to come and see me!!
His story is.... he forgot to cancel his POF account when he met me as it was free (hmm), he did reply to her email and text her, but never met up with her. He claims he is really sorry and is beating himself up over it etc, I've even had his mum call me saying she'd never seen him in such a state before etc.
So there you go - I'm in two minds, he should never still have been on POF and I'll never forgive him for that, but do I throw this relationship away because of it? Will I be able to trust him again? If not, surely the is no point in the relationship?
Love is poo.