IUD help!


I'm currently 18, and thinking about getting a good birth control. I haven't had sex yet, but I want to be prepared for when I become sexually active. I want to know which one would be best. My period is super irregular already, I don't cramp often, but when I do, its terrible. My hormones are already out of whack and have been since I was 15. I've heard the paraguard is non hormonal but makes cramps worse but I've also heard mirena and its sister brand makes you gain weight. Any advice or experiences would be great!