I am tired of being the "third wheel/single" friend?

I'm a 24 year old female and I have been really down lately about my dating life, or lack thereof. I have been single since I was 22, and before then I was in a long, three year, abusive in all the forms possible relationship so I did need time to heal, but now I'm ready to get back in the dating game, and I have absolutely no options. I have a degree and have started my career and I'm working on a second degree and masters. All of my friends are settling down or are in serious relationships and I'm still at point 0. Guys will look over but never come up to me (all my friends say I'm oblivious, but I also do not want to come off as desperate smiling and flirting with every guy in a place, but that is also what guys seem to go for). I have had a thing for one or two guy friends and I found out later (after they were already attached to someone) that they had a thing for me but thought I would never go out with them. One of my guy friends said "you are beautiful and nice, any guy would love to date you but most guys our age just want something else." It has me completely depressed because I won't just have a one night stand or a fling. I just want a nice, funny guy that has his head on straight. I don't care about materialistic things. I admit I do not flirt, but I am always very friendly to everyone and I laugh and smile all the time, so I'm very open to people. The excuse of guys are "intimidated" I think is not true because as "He's Just Not That Into You" (haha) says, if he likes you, he will ask you out. SO, why do I always find out when it's too late that there was an opportunity to date someone and why do guys not ever approach me or ask me out. I'm tired of being the third wheel!! Thanks for any help!