Well, I have two very distinct feelings about my I.U.D.:
1) Having it is one of the best things that's ever happened to me.
2) Getting it inserted was the one of the worst things that's ever happened to me.
I made the choice to get the IUD because I was having a really tough time with other forms of birth control. I'm a 20 year old with a four year history of struggling with birth control. I have an estrogen sensitivity ruling out most hormones, barrier methods were making me nervous, and the mini pill was a lot of work. I went to my local planned parenthood and sat down with an NP/Midwife for about two hours before we decided that the IUD was right for me. We talked through the pros/cons of Mirena vs. the copper IUD and I ultimately decided on Mirena and then scheduled the insert for a week later.
I was not, however, informed that if the NP did the procedure, she was not authorized to anesthetize me. No one actually told me that anesthesia was even an option for the procedure. Apparently if a doctor inserts it he/she can give you a lidocaine shot before the insert. You may have to ask for them to do this, though. I would HIGHLY recommend that you ask. For reference, a nurse walked up to me at a follow-up appointment and told me that she had given birth to 5 children, one without drugs, and the IUD insert that she had subsequently was worse than all of the births. That said, there's no baby after the IUD, which may have something to do with her less positive memory and it's worth noting that the discomfort (albeit extreme) I experienced after the insert lasted 2 hours tops.
The procedure, though, is fairly straightforward and relatively uncomfortable with lidocaine (and a higher dose of ibuprofen than I had taken). Tests were run to ensure I had no infections or STIs, then a preliminary gynecological exam was performed. They then measured my uterus to ensure that it was neither too small or too large for the IUD to sit comfortably and effectively, which basically involved them stabilizing my cervix and then inserting a small tube to measure. After it was determined that the IUD would work for me, they inserted a slightly larger tube to ready me for the actual insert. The way the inset works is really interesting. The IUD is typically "T" shaped, but the two arms of the T are folded up so that the device looks like an elongated I with two long, thin stings attached to the base. This is placed into a thin, hollow tube, which is slid into the uterus. The tube is then pulled out, allowing for the arms of the T to unfold. Then they cut the strings, leaving a little so that you can feel to ensure the IUD is in place and as a method for removal later.
As you can imagine, while fascinating, this can produce some SERIOUS discomfort. If at all possible, I'd recommend having someone you know in the room with you, especially just afterwords and I would definitely recommend having someone else to drive you home. Really, i've never felt anything quite like it...
That being said, I really couldn't be happier with the results. Though I experienced a light period that lasted a month and half just after the insert, I have since had 3-4 day cycles once a month that have been relatively cramp free. I will say that for a few days after, as I adjusted to the hormones, I was more emotional than typical, and I find myself more sensitive to emotions a day or two before getting my period. Aside from that, I've had almost no side effects, certainly nothing compared to my experience on the pill. I went up a cup size and have had a few minor breakouts, but that's about it.
Feeling safe to have condomless sex with my monogamous, fluid-bonded partner has been amazing and hot. The peace of mind and lack of human error the IUD have afforded me have been incredible. I don't really have to think about it EVER, and receiving a note in the mail informing me that I needed to renew my birth control in the summer of 2014 was unbelievably gratifying. It's awesome not to feel anxious about pregnancy monthly (however irrationally). The one thing I'll say, though, is you need to be even more vigilant to STIs. The IUD can intensify the likelihood that infection could impact fertility. But with regular testing, monogamy, and/or condom use that's easily addressable.
One last thing, some doctors, especially those over 50 (said my NP), are hesitant to proscribe IUDs to women who have not already had children because of complications with the first IUDs in the 70s and 80s. The defects have been addressed and multiple women's health organizations now endorse IUDs in younger women. There was recently a two part post on EmandLo.com that gives some more info.
Hope this helped!