First, I would like to offer my condolences on the passing of your mother. I recently lost my father a few months ago and I empathize with your sadness.
In relation to your question regarding classical conditioning and how you have experienced an emotional reaction to all things funeral related, I offer the following insight:
Classical conditioning is also referred to respondent conditioning and was made famous by Russian physiologist, Ivan Pavlov. The idea behind classical conditioning is that the subject (in this case, you) will repeatedly display a learned response (in this case, your feelings of sadness) as a direct result of a stimulus (exposure to items or events associated with your mother’s death). In other words, your emotional reaction to things which trigger memories associated with your mother’s death (e.g. hearses, funerals, etc.) is a conditioned response to what you experienced. To your subconscious, “funeral stuff” = “the pain of losing my mother”.
Bouton, M. E. (2007) Learning and Behavior: A Contemporary Synthesis, Sunderland, MA: Sinauer
Pavlov, I.P. (1927/1960). Conditional Reflexes. New York: Dover Publications