sweetie, emotions have no IQ, so stop beating yourself up for being illogical. :)
There are SO many reasons to have abandonment issues. If you love and like and respect this man, don't leave him, you'll just have the same issues with the next man.
Have you shared your fears with your honey? I mean, not in a "why didn't you call" kind of way, but a "Honey, I have to let you know that I'm a bit insecure and fearful of abandonment. I have serious abandonment issues. So if I get out of line or fearful I need you to be patient and understanding iwth me, okay? Sometimes all I need is a hug or this or that... and if you could help me that would be great, because the last thing I want to do is chase you away."
How you're going to deal with the issue is up to you, there are plenty of modalities for letting go of issues, from NLP to hypnosis, past-life regression, general psychotherapy and analysis, lightwork, affirmations, getting into a hobby with a passion, etc.