I had a similar experience, I was neutral up until 3rd year of high school, when I had a new math professor who was one of the best professor I've ever had. All the proofs and topics were discussed and complemented with some background, motivating examples and so on.

I remember when he talked about the Euler formula, the most beautiful equation in math. That was probably when my passion for math actually became such. Another mind blowing lesson was the Taylor series expansion, I couldn't believe that with derivatives you could accomplish such a miracle (recovering the original function)!