Why cant I settle???

Hi there, hoping for some advice. I'm a 38 yrs old Male, I'm healthy, consider myself attractive, and I have no problem getting women. My problem is I cant settle down and I'd like to. I had a long term relationship ( about 8 years ) and due to me taking a job traveling we fell apart and split on good terms, that was about 5 years ago. Since then I've been dating and a lot. I've dated great women that I could see myself being with long term but the minute it starts getting serious I find a reason to bail and run. I must be a decent guy because any of these women I run from continue to call and text and would take me back in a second, sometimes I go back to them because they were great but still I cant settle down. I'll go on dates, dinners, events, have them spend the night and really enjoy being with them, not just sexually but I have no emotions and as soon as they show some I run and move onto the next woman.... what's my problem?