He has refused to put a ring on it.......should I leave him?

 
I’m 38, reasonably attractive and keep myself fit and trim.My ex-husband walked out when our two boys were aged five and five months old, leaving me financially ruined. It was hard, but I forged a good career and now earn more than I ever imagined possible. My sons are fine young men nowWhen they were aged five and ten, I met the only man they’ve ever known me with.They liked him, but here’s the problem: 13 years on, he still refuses to marry me.
His father died 18 months later and he stayed on with his mother (now 86), although (with brothers and sisters) he’s not solely responsible for her. He has a good day job, keeps some livestock as a hobby, lives with his mother, who does everything for him, and has me to go out with. Good on him, eh? I do love him, he’s a good man who would never cheat and we still have an OK relationship despite many ups and downs.But I have been broaching marriage now for seven years and have ended the relationship more than once. The first time, he came back after a week saying OK, and we went to look at venues and engagement rings and planned our life in the. On the day we were going to buy the ring, his secretary (yes!) called to tell me he’d gone away early for his planned weekend on his motorbike. I cried for three hours, but took him back a month later.Last year, I dumped him again, and it was a similar story. We booked a romantic trip, but he said he didn’t want to talk about getting married and, once again, I let him get away with it. I cried in secret for fear of ruining the holiday. Now it’s June 2013, and I know I must find the strength to leave him. I know after the initial hurt I could get my youngest to uni, then take up my firm’s offer of a year in America. But why do I worry about hurting him more than about how much I  am hurting?A guy at work (53, recently divorced, two adult sons, and rich and posh — which intimidates me) asked me out to dinner. He seems nice, very intelligent and I wonder if I should give him a try. I’ve not felt like that about anyone else in 13 years. Or maybe I need to be on my own for a while. My best friend says I should have dinner with this guy, but why (after everything) does that feel like cheating?
ABIGAIL