I know (pretty much) how you feel, and I can totally sympathize. I, myself, am a hopeless romantic. I want someone I can nurture and be there for and grow old with, not just some...Hollow, energetic fling. I, too, am 18. --Believe me, nothing you've said that you want is childish. People 5 times our age, sadly, feel similar things. I, too, have had so many friends, who then just...Have more important things to do, who have other commitments, and you just become a fly on the wall for them. Such is life.
I, too, want someone to want me, someone who wants to explore my heart and my soul, every nook and cranny, find out exactly who I am and what I think and feel. That nobody has a magnifying glass at hand, trying to do so, is discouraging. Certainly.
Doesn't help that I don't have much of a base. I have my best friend, I have a good friend (who lives in the states), but beyond that, not really anyone to talk to about my own problems. I don't have any sort of religion or group or anything to seek guidance from or find solace in (not that I desire the former). So yes, it can be stressful.
But I don't let it consume me. Love has a way of...Finding you. Just take your life a day at a time. Try not to worry about it. As silly as it sounds, I pulled out my hair worrying about relationships for a year, and it got me nowhere, and now I'm just (mostly) not worrying anymore. Still have lots of time.
If you need someone to talk to, feel free to message me! Hope you're feeling better soon. It's stressful as all hell, demotivating, I know, but it'll be just fine. I promise.