cant ever get a girlfriend no matter how hatd i try

Hey your 18! you are still young! and it also sounds like you find it easy to make friends with girls, that can work in your favor if not now then it might come in handy later. Hang out with these girls as friends, dont think about having a relationship with them just have fun and learn from the experience. Keep them guessing, dont ever come on too strong or eager first and you might find that they start chasing you instead.

Hi Brad!

I can feel for you & I know exactly what your problem is, because I have been there! It happens to quite a few guys in the way that you describe: you meet a girl you like, hang out with her, try to get it to the next level only to be stonewalled by almost a similar line every time, just as you described.
When a girl says to you that you are sweet & she wants to be friends, this basically is a very nice way of saying: I am not attracted to you.
It seems to me you do not know how attraction works for women, so I recommend you read up on that.
That she says she doesn't look for somebody right now, is not accurate. I would never call it a lie, because it is not. Maybe she even believes it herself. But in case that she is single, and a man comes along that she is attracted to, she will give a s@$% about not wanting anything serious at the moment, she will gun for him!
And with attractive I do not mean good looking, women work different than men on this. With attractive I mean a well grounded, confident & strong man.
As for the little that you describe about your situation, I think your problem is that you are being too nice to girls. You make the classical mistake of being the Nice Guy. Women are not attracted to nice guys, because they see them as pushovers that display too many feminine qualities. But that is not what they want. They want to feel feminine. In order to do that, they want to be around somebody who has very masculine qualities.
Now I am not talking become the bad boy here! Don't start to treat girls badly. Rather, stop being the nice. Challenge them, give them a hard time sometimes. Develop Confidence in yourself! Learn what women are attracted to in a man & what it means to be a real man. Start taking the lead. Like in any dance, where the man takes the lead, so you are supposed to take the lead in getting a girl from liking you to being your girlfriend. Don't let her lead...you will put her in a position she does not feel feminine in & she won't see you as a man that has his things together and can protect her.
There are some great materials out there and I am happy to share them with you. I will not post them here, because it might be too spammy, but you can send me your email and I will let you know!

Here's the problem. It seems like you're too nice. I know it sounds weird but it's true. We dont like guys who are easy to get..

There's so much time for you. 18 is nothing. Just keep practicing being funny and expressing interest in women subtly and you'll start to see results.