depressed and sad

I am so depressed and sad, I am 25 years old, and I am a nice girl, but I don't know what does that feels have a boyfriend, all the guys I met, never took me seriously, and now I just Belive that I am not going to have a real boyfriend never, no one is going to fall in love with me. Guys just used me for sex . Now I just want to kill myself, I feel so alone and I don't believe that my life have any meaning.....