You're right that those scary stories can be hard to ignore. In fact, because so many people find them hard to ignore, we actually wrote a piece about them that you might find helpful: Have a Little Faith in BC
As for the IUD, this is a great starting point for the information you might be looking for: Intrauterine Devices (IUD, IUC or IUS)
. Since it sounds like you're leaning towards an IUD as an option, it may help to know that some of the things you're worrying about, like it expelling itself, are far less likely to happen then, say, forgetting a birth control pill at some point. Too, if it were to expel itself, you'd see it and be able to address the issue quickly.
With birth control options, it sounds like effectiveness level is really important to you, which would make the IUD a good option. There's also the shot ( Depo-Provera (The Shot)
) that has a 96% effectiveness rate with typical use (and if you backed up with condoms you'd be in good shape). Is that an option that interests you, or are there things about it that don't sound like a good fit?