Please go to another doctor, the sooner you fix yourself up, the sooner you will be happy about yourself and your life.
I've always struggled with my weight and had the same propblems at school as you have said so I know how you feel. I managed to get a bit of weight off so that I am happy. I think being happy is one of the most important things you can have in life!
Just tell the new doctor that you were seeing another doctor and you were up to the stage of discussing seeing a physcologist. Tell the new doctor that you have found one, but you just need a referal. The doctor should have the details on file which will say why you have been to the doctors the last few times. I'm sure they will understand. And the doctor wont laugh at you!
Fix yourself, take care of yourself! And be HAPPY!
HTH
Tally.