CarpeDiem,

Most if not all people find it a real challenge to do meditation, myself included.  There are several different forms of meditation.  This form I am recommending is just to focus on your pain/anxiety/obsessive thoughts and where it shows up physically in your body.  Stay with those sensations and breath into it for some amount of time.  Usually until it goes away but if it doesn’t then just for so many minutes you care to do.

It is good to have a routine, a place, and a regular time to meditate. For your ex-girlfriend issue, try whenever you start thinking about her; notice that you are thinking about her, stop, notice where in your body it is showing up as a feeling, place your hand there, and breath into it for a bit.

It may not be a formal meditation but it is a technique to deal with the unpleasant thoughts and sensations that is keeping you from moving on to living life in the present.

Mark