Honestly, you sound like someone who is overly dependent or possibly co-dependent with this guy. I know this from personal experience that it's not an easy task to be more independent, especially after enjoying the intimacy of codependence, but this is something that will inevitably make you a happier person.
It's great that you're mindful of your own feelings, especially your paranoia, "clingy"ness, and sense of abandonment. It's important for you to vocalize these feelings for yourself and start some kind of acceptance of what you can change in your life, what behavior you can control in yourself to improve your life as it is now.
Get interested in other people and stop blaming yourself for his leaving. This is not your fault. This is not his fault. It was just what happened. You can let yourself get over it by simply accepting what is over. The past is in the past. Give yourself some new goals and start concentrating on an acceptable future. Make sure the goals hinge on things that you can control, like stuff that you can actually accomplish with very little help.
Good luck, and start living again.