Docs can you explain, is the dentist incompetent if a filling falls out 3 times in a year?

I won't go that far: It really depends on how big a filling is, on which tooth, and your bite. The dentist may be trying to avoid having to make a crown for you. Small bonded restorations on the edges of your front teeth chip off easily due to occlusal forces. Don't be so harsh.. Ask him/her for an explanation. If you are not satisfied with the response, seek a second opinion from another local dentist.