There have been plenty times where I'd struggle to find a date or relationship and I'd feel undesirable or some people would be under the impression that no one wants me but the reality is, there were women interested me during that time, I just didn't like them back. I think there's a huge difference between the two and anyone going through it should realize it so it doesn't hurt their self esteem/confidence.
Remember Harold and Kumar Go To White Castle where Harold's main issue was with getting a woman. He said the only girls like I have no interest in me and the only ones who like me, I'm not interested in. While that may be true during a specific period, you shouldn't let it deter you from trying.
Another thing about that is even if the only ones who like you, you aren't interested in then you shouldn't settle. It shows you have little self respect and it doesn't make you happier plus it's unfair to the other person as they may have genuine feelings for you. You should date someone because you like them, not to impress others or just for the sake of having someone.
All I can say is keep your chin up and keep going until you eventually find someone. Not always easy and the time can vary for when it happens but at least you're trying.