Hi,
You are confused about the contradictory feelings you have about your maths teacher. You must remember that it is illegal for a teacher to form romantic associations with his student. Going up to him might indicate to his collegues that you are falling for him. He does not want to put his job on the line. It is right and proper for him to report your approaches to his superiors. Nothing to do with betrayal.
If you have problems you should go to the head teacher and he/ she may refer you to a counsellor.
Your dream could have been caused by some physical upset, however falling in love with your teacher is probably the cause. Look to someone your own age.