Dont know what I want what's bothering me !?

I think you are simply young and want to play the field. You're a player! ;) Enjoy being single and dating different people. Sow (sp? ) your Wild Oats. Just be safe physically and be careful with your and their hearts, be respectful and honest. And don't beat yourself up. When the right girl comes along, you'll know it and your feelings will last.

But, cut yourself a break, you're 18 and you have plenty of time to figure out what you want, who you want to be and who you want to be with.

(God I feel old! ) Enjoy!

You are confused, you're having difficulties differentiating lust and real feelings. I think you are just trying to find the right girl for you and thinks that every new girl that comes along your way is the right one. Try your best to differentiate who among those girls you'll miss most when gone.
I think you have a tendency to get bored if you stick to only one girl. If you continue to do this, you'll get girls to talk about you and say that you are player and they might start not to trust you.
Gather your thoughts and learn to prioritize who among those girls you'd miss most and stick with her. Stop going out with all of them, one girl at a time =)