1980's? YA? Romantic Novel

I read a book in the 80's as a teen about a young man and a girl, for some reason I have a carnival in my mind, made a pact or a promise to always stay together. This brain has been through cancer and chemo and I now have a daughter and this book (amongst many others that of course I can remember) have stayed with me, this one however haunts me as I have searched google, msn, amazon. I cant for the life of me think of the name or author.

Maybe Forever by Judy Blume? The main character and her boyfriend make a pledge to always stay together. She later goes away for the summer and becomes attracted to another man. I think there might have been a scene at a funfair or similar, though I'm possibly confusing it with another book.

Long shot, but aside from Forever by Judy Blume I'm also wondering about Endless Love by Scott Spencer, which was turned into a movie starring Brooke Shields.

Thank You konallis, I will look at that one. It was obviously a YA/teen author but in the 20+ years its been since I would have read it, my brain has been fried and gotten a lot older...LOL. I just remember it touched me but the amount of books I read then and the amount of books Ive read since seems to make some run into each other :) Thanks again. Crossing fingers