Copper
"
Had it put in two months ago. Insertion was a mildly unpleasant experience, but not bad. I went to the library to work right afterward. Cramped every few days for the first month, but I haven't felt anything this month. I still use condoms here and thats out of paranoia, but it's amazing to (mostly) not worry about getting pregnant. I've been recommending this to my friends. Just be sure you have a good doctor with lots of practice inserting IUDs.
Hypochondriacs might want to use a birth control method less easy to use as a scapegoat for every headache or tired afternoon, though."