I'm afraid Rose it could be receding gums, have a word with your dentist about the type of brush & also the way you clean your teeth, do they bleed when you clean them?
I had no problem with mine & apart from having my wisdom teeth removed because they were to big for my mouth & pushing against my other ones, I still have all mine & only one filling, so I would agree with i love to patch ^^^^^ !.
Do you smoke? That also can damage teeth as we grow older, it sounds to me that your tooth is perhaps not as firm & that's why infection is setting in?