We'll start with some definitions.
Stereotype is making general assumptions about the members of a group irrespective of individual differences.
Prejudice is a belief of feeling of dislike for a particular group.
Discrimination occurs when this prejudice leads to actions that cause harm to those prejudiced.
Racism is a form of institutionalised discrimination that becomes perpetuated throughout society.
Given you don't harm or have a negative belief about other people based on your preference, it will not be classed as discrimination or racism. Besides, you have the right to choose who you want to be with.