Any thoughts on this would be appreciated.. to make it quick.. gf and I had a break in Feb... our relationship although full of a lot of good moments had its issues... primarily she was a communicator and I, not so much. I would be so hot and cold with her that she eventually became disuaded (I believe) to try. Anyway she asked for a break and I of course at first went along with it but within a few weeks into it was pretty much begging to get her back (I know, bad move but was what I perceived was right at the time)... so pursued her then left her alone... and when I had by April she was coming around and had expressed feelings of missing me and stating that she wanted to talk about reconciling our relationship... I feeling hurt and over confident began making demands on the relationship before we had even talked about amending.. well that resulted in a blow out... and now I hear she has been dating a co worker since Jun-Jul.. this guy I knew had been lurking in the back ground and had an interest in her from day one... anyway.. since then she has called a mutual friend of ours(someone I had introduced her to and a longtime friend (girl) of mine) to wish her happy birthday.. had even made plans to go out with her then cancelled. She then had called me 1130pm one night in Jul but hung up.. I called her back the next day and she stated it was a mistake but wanted to know how I was doing.. I was short and cordial but was like okay!. Then in begin of August I bumped into her on the street and she was acting nervous (naturally) and began telling me that she meant to call me about some pictures I left at her house and began a big to do about how they were so cute etc. and how we should meet to have a coffee and so she can give them to me. I played it cool and didn't really say anything other than OK, because she has made that coffee promise and other promises since our break but has yet to keep them. Plus I find out that she has not removed my phone number, family phone number, email anything from her phone.
I guess my question is this a rebound thing with this co worker? I'm not stupid in thinking that there wasn't some ground work before by this guy, but I do know for a fact that she hadn't acted on anything until we broke, which is her right. But I do love this girl and I want to know whether this guy who seems to be filling all her needs right now has a chance of making this last? We were together almost two years and have been through a lot together in that time, just hard for me to believe she can move on with this guy so quickly.
I'm staying in no contact and have recently started to date lightly to start moving on so I don't want anyone to think I'm pining at home all day. Just thoughts on this would be nice. Thx all.

My thoughts are that you should forget her as your whole post is full of her thoughts, her actions, and it only shows you are holding out hope to get back when she gets done with what you hope is a rebound, and whether it is or isn't, you need to let go of her, who no one here knows, and get your own life, without her period. Sorry to be blunt, but read the other posts in the relationships forum, and you would know, you are not the only one having trouble letting go.

Continue with no contact and start getting busy with your life. You are still really focused on her as Talaniman pointed out. You need to start trying to move on she has. Also it doesn't sound like she moved on so quickly basically your relationship has been over since February. I'd say for her to have began dating someone in June or July was waiting a pretty good amount of time. She clearly spent that time healing why have you not done the same?

Sounds to me like your pride is bruised more than anything else, that somebody stepped in and took over where you were sloppy.
Get over it and move on, and learn your lesson. Don't take your lady for granted, there will always be someone waiting in the wings.