So it turns out that my family dentist DID mess up a filling. He didn't fill it "deep" enough, so it was really thin. The dentist today told me that over the years, when I put pressure on it from chewing, the tooth was under too much stress that wasn't supported, so eventually it chipped off. Luckily, it was only a tiny part of the top part of the tooth.
They couldn't fit a normal-sized xray in my mouth, hahah! I had to use a kids' sized one. (My old dentist used to bend his to fit them in... hrm. that sounds off now that I think about it) Then the guy kept poking the tooth and I could feel it moving. The dentist went back to chatting with me, and a few mins later when the xray photos came in, he opened his palm and said "by the way, here's the piece that chipped off".
I'm so glad I didn't feel it, or I would have cried my cowardly azz off. I'm so bummed now that I have a broken tooth. He filled it with a temporary filling and I can go get it re-filled.
I wouldn't be so bummed if my tooth broke because of MY stupid mistakes or whatever, but it wasn't even my fault! grrrrrr.