How can I calm down and say 'yes' to a guy?

I have had four guys ask me out this year and I said no to all of them and I liked one of them but I don't know why I said no I can't get my self to say yes to anyone. Plus it would be first boyfriend but I cant get myslef to say yes, I guess im scared....

how do I calm down?

Ok...I'm assuming you dated these guys and they each asked you to be exclusive? But you are not ready to be exclusive? If so....its simple this...you have not found the right one, the one who you feel you are ready to make the commitment to just focus on him and no one else.. you sound like a smart girl....some girls just think they have to have a boyfriend and cant stand the sounds of being single. But for you....you are selective...and one day you will know he is the right one you want to invest your time and energy with....because, relationships do take a lot of work and time to make things go right after the new relationship energy has disolved a bit...don't worry about your past decision, they were right for you at the time. Now the one guy you did like, why don't you try to reconnect and maybe it will work....but always take your time, take things slow to make sure they are right for you...and him. good luck!