Hello, Is It Okay To Have A Horizontal Space Between

hello, is it okay to have a horizontal space between upper and lower teeth? there is space about 2 - 3 mm i can protrude tip of tongue through it when my jaw closed, and i can bite a piece of paper and pull it like with no force !! i'm wearing a braces i told my dentist and he put a lower reverse curve and changed it 3 times NO improvement !!