I was really into this book that was about a love story between two teens. I think the boy’s name was David and he had a St. Jude medal or necklace that was part of the story. One of the couple may have been ill. I can’t recall if it was a happy ending.
Not “The Beethoven Medal” by K.M.Peyton? The boy is called Patrick Pennington, and is training to be a concert pianist. The girl is called Ruth.https://www.amazon.co.uk/Beethoven-Medal-K-M-Peyton/dp/0690128460
Maybe Sex Education: A Novel by Jenny Davis?