Why cant I get married?

I am 33 years old and every relationship I get into the guy always seem serious to settle down at first and then changes his mind. I wonder. I have always dreamt of an early marriage and have always worked towards that. I have been having relationships since I was 20 and every one I take seriously but the guys just seem slippery, always finding faults and always judging me wrong. Then I became cold and started pushing them away long before they even say 'I love you.' But now I am worried about my age and do not want to wed as an old maid. I hope to get married soon before I clock menopause. Please tell me what is wrong with me and why I cannot get married.