Poor you - what a awkward situation. As Midnight Blue said - I can only tell you how things were for me.
Around this time last year I broke up with my long time boyfriend. He was and is a wonderful person who just wasn't right for me. It took us a while to disentangle ourselves from each others life. (After 5 1/2 years we have a lot of mutual friends and way too much of each others stuff). In a way losing him as a friend was a lot harder then losing him as a boyfriend. But I knew that it was too raw emotionally for us to keep seeing each other on a regular basis. Resentment and blame would have cropped up and my memories of him wouldn't be as nice as the ones I have. I still feel sad that we're not friends but know that he's moved on and I'm now seeing someone who is right for me.
I did regret the break up for a while but I think that deep down I knew it was for the best. Just after all I could think of was the fantastic times but I ended up with a list of things I hated about him to stop be from wearing the rose tinted glasses. Do you think you could be doing the same?
The other thing that springs into my head is could he be (sub consciously or otherwise) trying to punish you for the break up? Or at least make sure that you regret it. Or maybe he's scared of hurting you and doesn't realise that you're capable enough of surviving without him.

Feel free to ignore my advice, but this is what I'd do:

Write a list of anything that he did that you didn't like.
Remember your reasons for the break up.
Mourn for the relationship. but.... (and this is important) give yourself a time limit on wallowing. 24 hours to think, talk and remember but after that start taking steps to move on.
Try to be busy. (If he comes around in the afternoon then arrange to meet some friends in the evening. And let him know that you're heading out and have a deadline)
Show him that you can cope without him.
If you want to get back together with him remember that there is no rush. One friend of mine married her old boyfriend..... after they'd split up 10 years before and been married to other people. If it's meant to happen then it will.
Sorry for the length of the post. Started writing then couldn't stop.

Hope you find something to cheer you up soon xxxxxxx