The answer to your question is completely up to you. I highly doubt you are as bad as you say, your self-esteem is currently at an all time low and so you are in an ever ending spiral of self-criticism and loathing. Trust me, been there, done that and it sucks. Do you know what changed all that...my attitude.
Start saying how good you are. List on a piece of paper all things that are good about you. What do you think other guys are offering women that you can't ay? Nothing. The difference between you and that guy you see getting all the girls is a brilliant act of confidence. If you think you're brilliant, so will everyone else.
My brother used to say the same as you, he found his wife when he was 30 years old and hasn't looked back since.
Number one, get out there. Go to as many things as you can, join as many clubs as you can. Get an active and varied lifestyle and start to enjoy yourself. What do you really like doing? Find out and go do it. Life is too short for us all to sit around moping and hoping someone is going to come a long. She is out there for you, waiting, and you need to go and get her.
You say girls ignore you, well ignore them back they aren't worth your time. You're acting as if you are inferior to them, well you're not. You are a human being too damn it!
Now come on get a bit in fight in you, find that girl, and she will realize she has something special.
I can guarantee you will look back on this question one day and say to yourself 'what the hell was I thinking'. Good luck :)