How long have you been single?

I've been single for 2 years! I'm so annoyed, I have dated between then, but none of them worked out obviously. I know this is the time for me to focus on myself and education, I do want to accomplish a lot before I get into a serious relationship. But it's hard sometimes I think there is something wrong with me, like why can't I have a nice man in my life that I actually see a future with?