37 year old male with a lousy dating history - HELP!?

Starting off I just turned 37 and I am very shy and it is very hard for me to even make any friends to begin with. Then to top it all off I have dated only 5 women in my life, all of which are after I had turned 25. None of the relationships ever made it 6 months as I was used plus I was told I was clingy even though some have told me I am not clingy. Other than being shy I have been morbidly obese most of my life but I have been working hard on losing weight this year and will continue to work hard on losing weight. However, it has been 3 years since I have been in a relationship and no woman will ever give me the time of day. Despite the fact I have never been picky in searching for women the dating sites are not even giving me any results at all. Is it too late for me to ever find a romantic partner? If not then what should I do? If so why is it too late?