Why i can't find the right guy?

I think i have a serious problem..
I am 23 years old girl and i’ve never have a boyfriend before.I am told by my friends that I have really high standards when it comes to dating, and that’s why I never meet anyone. I am not an ugly girl..I just never interested to have a bf to take the relationship seriously thats the reason…Now i care with the result and i am so confused. I am not a conservative person in life and i do flirty things all the time and it works…but the result is never complete..I really wonder what is the problem? What might it would be the reason? I feel guilty thinking about how ugly girl have a bf and i dont….thinking about it makes me more uncomfortable.
On the other hand i really attach importance to study my school subjects and exams..When i feel miserable everybody thinks that the reason why i feel like this might be my subject and try to relieve me. But they dont know the real reason why i feel like such things!! I do care about my love life ,i do care about everything which effects me!!
What can i do? Please dont try to lighten me up! Because it never works..All these years i did think positive but it couldnt help me to get through it and never it will…Please tell me where am i wrong? What is the occasion?…I really need your help because i am disappointed these days..And i cannot find the way out!!!