How do you start to date again when anyone who shows interest is blown off because she is not my ex?

You are so not ready to move on. This thing with your X is not resolved and you would be being extremely unfair to date anyone and expose them to this attitude.. in fact if it was someone who's feelings for you were true and genuine you could cause some horrible internal scars that she wouldn't deserve. What you need to do is either see if you can rekindle what you had with the X or seriously GET OVER HER... I understand where your thoughts are coming from but they are wrong.. in time you will see that.. if she were "perfect" for you she wouldn't have the title X. Don't inflict this upon some innocent woman.. deal with your feelings and get back to normal before you date someone new.. it would honestly be cruel of you.

You start by forming an intention in your mind to call someone you know to ask them if they want to go on a date.

I hear ya! So I am trying to get back with my ex again since meeting others so far (for past 3 months) hasn't done anything for me. It sucks, but maybe that calls for another chance?

You need to somehow get over the past to go on with your future!