Did you clear over the primer?
Was it your intent to build the car with an 'in primer' look? If so, forget the clear coat.
Was it your intent to finish the car in gloss grey? If so, I see a couple problems. First, lots of junk in the finish. That will be a factor of your painting environment, and perhaps the windy day. Also, before applying the clear coat, rub the primer with 1500 grit sand paper, then wash thoroughly, blot off most of the water with a lint free cloth and let air dry thoroughly. Before painting, give the surface a quick wipe with a lint-free cloth wetted with alcohol.
This finish can be saved with a little wet sanding and reapplication of clear.