I have been with my partner for 8 and half years and we live together There had been some problems in the relationship last year after I found out that he had cheated on me while we were on a break for 4 days. He didn't tell me about it straight away only saying that he realized he didn't want to lose me when he came back. When he did tell me months later I decided to forgive him but found this hard as he was working away Monday to Friday and when he came home he would often go out with his friends and I wouldn't see him. I did give him an extremely hard time about it but eventually did forgive him.

A few times he had told me he wasn't happy but didn't know why. When I asked what I could do he didn't know and would reply he wasn't sure of what he wanted anymore yet he would always stick around and I did whatever I could to try to make him happy.
I did find him quite sneaky at times and I couldn't help think that maybe he was seeing someone else after what had happened last year, he always denied this.

Last week I came home from work one day and found a note in the kitchen informing me that he was going to his place of work where he has a flat as that was where he wanted to be and that I had to move on. I was devastated and he wouldn't take my calls.
I've since found out via the joys of social networking that he has been seeing the same girl that he got with last year, she's been asking him to leave me to be with her but he previously wouldn't. However the day he left me I've found out that he went to the flat with her for the weekend.

I'm absolutely devastated and I don't know what to do with myself. I've been off work all week as I've made myself ill with it all. I don't know how he can move on so quickly. It doesn't feel like my life and I miss him terribly. I just can't help but think if she wasn't on the scene that we would be OK, he was never going to be happy when he had another option.

He hasn't been in touch and I've given up trying, I'm desperate to get in touch with him but relations are really bad at the moment, its just really hard and I do miss him as he's been a massive part of my life. Part of me wants everything to be OK and the other part of me thinks its unforgivable what he's done although I'm not sure I have a choice in the matter at the moment, all I do I know is that I can't stop crying or thinking about it or him.

I can't seem to accept that its over and I just don't know what to do next...

This is probably not what you want to hear, but at the beginning of your post I was thinking that you should give him another chance. I mean you were on a break. The hiding it from you is wrong, but it is something you can work through. Then, after reading the rest about him still talking to this girl as you were dating... sounds like you should find someone better. Someone who is committed to being committed. I know it's hard, but surround yourself with friends, get out and have some fun. He sounds like a jerk.

I know this is devastating, and you deserve to cry it out of your system, all I can do is give you a big cyber >HUG<, and hope you get more from friends, and family. Maybe see your doctor for some good advice and help as you get through this (and YOU WILL), and in time you will see this for the blessing that it is.

This door will close, and another will open for you, and WILL be better.