I had this problem with my molars, primarily, though other teeth were affected. Dentists I've talked to (and that my mom talked to when I was a kid) tended to link it back to a really high, sustained fever I had as a toddler, which likely affected the development of those particular teeth. (Edit - antibiotics prescribed for that illness may also have come into play. It's really difficult to pin it down, and in some respects not that useful an exercise--the damage is/was done).
Here's my experience. Bear in mind that I'm in my 40s and that dental technology and methods have progressed quite a lot.
When I was a kid, the bad/weak enamel on my molars caused a lot of sensitivity to acid foods (citrus), chocolate, and to the slightest touch of a fork. The surface of some teeth is apparently also sort of uneven. Two of the teeth were given big fillings; two others were crowned. Years after the crowns should have worn out or whatever (they were stainless steel, and according to my current dentist, were never intended to last 30 odd years), I had them recrowned with gold.
I have some discoloration on my front teeth, likely caused by the same thing. If I were to finally (after all this time) have that dealt with, the main issue would be to be as non-invasive as possible and that any whitening agent would be formulated by my dentist with my teeth in mind.
For years (until I was about 32), I never had a cavity, then I had several at once (which irritated me), then none again (I'm closing in on 47). One thing to know about cavities though is that it's important to treat them, because the weakened enamel can cause them to get bad/worse more quickly.
I use toothpaste designed for sensitive teeth now, but didn't as a kid.
Based on my own experience, don't beat yourself up over this, and don't worry too much about it. Regular dental checkups and monitoring will hep you stay on top of it. If I had to wish my parents had done something differently it would be to have had them teach me about flossing and really nag me to develop the habit. Because I don't think it ever came up.