I don't understand

So I've recently turned 18 and I've been so unreasonably like.. scared almost? I tend to find myself liking the idea of younger.. (like 13, 14) I'll start off by saying that since around 7 or 8, sex was a big craving of mine and it's been that way since. I even asked people if we could have sex around then and obviously I didn't. But I wanted to even as a kid. I can't necessarily say that there's anything different in my prospective about sex since then either though, I've always kind of seen it as something that just feels good and do with someone you love and trust. I understand that most people are concerned about maturity and things like that but- I don't know I feel like as long as they understand what they are doing and why that's all there is to it... I've most definitely seen some unmature adults- I don't really understand why it's made out that sex is like... some big deal that'll change your life 😅 I've literally only seen it as something that makes you and someone else feel good, if they understand that and understand that they are allowed to say no, I just don't really understand or see a problem... is there something I'm not understanding or something wrong with me?