I had a horrible experience with Mirena. I had it for 5 years with no problems, however it was after I had it removed. Google "Mirena Crash" before you make that decision. Yes it happened to me. I would go with the paragard iud, has no hormones and I think it's good for 10 years and you can have it removed at any time. Good Luck! :)
That depends on your health, your own personal choice and the level of commitment you wish to take. Personally, when i was in my 20s, the pill worked fine. I hated the patch and the ring had issues too. In my 30s and with kids, i didnt want or need something else to think about so the depo shot was my best bet. I have friends who love having Mirena. They are also younger like you and a longer term birth control is more justified.
I personally had my 4 children ages 6 8 9 and 11 and im 31 weeks preg. For me im glad that I had them so close so that they can grow up together. .and also leave together:)...not saying this is the best for you..but it was 4 me...I hope this helps.