Love Lost

Ok well am 16 years old and i have never had a girlfriend in my life, its not cause am ugly. i have been called a good looking person before and i have had girls liking me but for some reason .everytime i get close to a relationship with a girl that i do like. I CHOKE! i know they want me to ask them out because of flirting that happens between us and how nervous we get when talk to each other. I guess am scared of losing the person by her thinking am boring, a loser, or a just not worth going out with me anymore...if we do go out? I want it to last forever but i know youre first girlfriend is not likely to be with u for that long. Like my recent problem was when i got really close to asking my crush out. Which i knew she wanted me to ask her! She waited for me to ask her plenty of times (3 months). But on valitines day i deciced to give her a card with a rose. expressing what i would do if i was her boyfriend! But i didnt write my name on it instead i wrote "sincerly from you secret admirer" after i turned the card to my high schools office, which were going to give it to her, in one of her classes. Well after school i told her "just from curiosity lf she had a boyfriend" and she said "am not single because am waiting for my secret admirer to ask me out"!.....

The very next day, she waited for me to ask her out already because i notice her glancing at me more than usual and her friends giving her space if i did go up and ask her out but again i choked! And after class she took the valitine card and threw it away :( since that day i havent talk to her. What should i do??!?!!! :(((