You're 40, so you're past the age of wanting to have kids (most likely). Do you typically go for younger women who are at that point? Who are you dating? Do you have a "type" of woman you are dating that keeps dumping you? Are you shooting for a 10 when you should be going for a 6 or 7? What are your actions when you are dating? Do you call everyday (creepy)? Do you text incessantly? Do you drop everything to spend time with her? Do you have a life and hobbies or do you spend all of your time searching for "the one"?
Do a little introspection here.
From a woman's perspective, its kind of creepy when you find out the guy you are dating has never had a long term relationship, but has "always wanted one". Someone who has found 4 women they would like to marry in the last 10 years, yet who has never had a relationship for over a month, has some serious soul searching to do.
I can't speak for all women, but I do know there are things I look for in a man that make him more attractive as a mate/partner:
1) is he driven, does he have goals, has he achieved said goals?
2) does he have secure employment (yea, it's cliché, but I don't want to be the one paying the bills)?
3) Does he have long time friends?
4) What are his hobbies, is he willing to share the hobbies he has?
5) Does he have a solid relationship with his family?
6) Is he planning for the future? Does he have a retirement plan? Does he know about investing?
7) Does he have a pet? Is he responsible?
8) Is he clean, does he take pride in his appearance?
9) Does he eat well and drink in moderation?
10) Can he hold an intelligent conversation WITH me (or does he do all the talking)?
Obviously these aren't all the things to consider, but they are things that I know I look at.
There's a lot that goes into a relationship, one of the main things that will turn a girl off, no matter what is the "creepy" factor. There is this leer that some guys have, that really creeps women out. No amount of money or material possessions can eliminate it. If you want to know what it looks like check out Millionaire Matchmaker, its the episode with the duck embryos (that guy still gives me the creeps).
I could keep going on what makes a man an attractive mate, but I think you get the drift. And to end with my favorite expression: "Be the person you want to find"