Dealing with severe anxiety over BF's ex

I am an overly emotional person and am plagued with anxiety, fear of abandonment, and insecurity issues. For the last two years I have been working hard to build my self confidence and conquer these debilitating problems.
I met this guy who was just ending his ten year relationship with his ex... Soon after we started dating...( my stupid move for jumping in so quickly.)
We have been dating for a year now and I recently found out that he has been emailing and talking with his ex this whole time. The nature of the emails are flirtatious he definitely leads her on...
We have spoken about it some. He says that up until recently they were planning on getting back together but now he says that they both have decided that its better for them to take time apart.

Anyway, today he is having dinner with her. He tells me that there is so much history there that it is going to take time to process it all and that I need to respect that. So I'm trying to play cool....

... I'm hurting though. I really fell head over heels for this guy and I feel like I'm being used... But I do know that he does care about me. He is not one to say I love you or a whole bunch of words though and that leaves me with unsettling uncertainty.

Is this me jumping to conclusions and stressing over something that I have taken the wrong way?
I know I have a lot of work to do on myself with or without this guy....
Help.