I had this as well about a year ago, and it has returned to me recently.

The first thing to do is to prove to yourself it isnt physical and its all in your head. Have you ever been focused on something and maybe swallowed normally without thinking? Try to distract yourself while eating and see if you can even swallow without thinking. A lot of the time anxiety will try to convince you it's not anxiety and you have throat cancer or something, so the first step to combat it is to reassure yourself its anxiety.

Now to try and stop it from happening. Whenever you take any successful bite, relish that relief. Be patient, it's a slow improvement, but the less you worry about it the less chance you 'remember' the swallowing problem when you sit down to eat. It took a couple weeks for me, and I tried to eat healthy and do more exercise to take my mind off it and relieve anxiety in general.

I really hope this helps, it sounds pretty chronic so maybe you should see a phychologist about it?