Im thinking of a song....?

I dont really know any lyrics so you'll hafta be good to get this one but its a song that sounds like its maybe from the 70s or something...and it talks about how a girl has a boyfriend but they're having problems and the guy singing wants to take advantage of a situation because he "fell in love" with the girl that hes singing about. some of those might be direct/paraphrased lyrics so its not as vague as it sounds. any help would be greatly appreciated =)