Rapport with your teacher and expectations being the same are the two most important thing I can think of in having a successful teacher student realtionship. It seems to me both were lacking in your first two CFI's. If the third one does not work out, I would think long and hard about why it is so hard for you to learn the basics of flying. I would suggest that there maybe a common theme between these issues of fustration with fustration in learning other things such as scuba diving.
Good luck, don't give up.
Doug
