Using had vs have in a sentence

tenses past-tense have

For this sentence, I'm not sure whether to use had or have:

Ever since I saw Harry Potter, I had/have been interested in Muggle Studies.

"Have" sounds better, but "had" and "saw" are both past tense.


If you were interested but not anymore:

Ever since I saw Harry Potter I had been interested in Muggle Studies. But then I read a little bit in a Muggle Studies textbook, and I'm not interested anymore.

If you're still interested:

Ever since I saw Harry Potter I have been interested in Muggle Studies. I'm hoping to enroll in Muggle Studies when I get to college.

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