How could my BPD ex stay with me for 21 years?

[Family Court Strategies: When Your Partner Has BPD OR NPD Traits.]

I have been reading on BPD for about 6 months. But there is one thing I cant explain. How had my BPD ex managed to stay in a relationship with me for 21 years? and why? It is a very long time. He betrayed and told lies (during the relation I didn't know them), he played the hot-cold game constantly, he was a great lover, then a terrible one etc.
Most of the time, our friends adviced me to leave him, but I believed in him and the connection we had. Finally, he left me and said he was in love with someone else. Life is a big fat joke. I hate missing him.
I need any ideas about his staying with me for so long... .Thanks.

[clytie]

I have been reading on BPD for about 6 months. But there is one thing I cant explain. How had my BPD ex managed to stay in a relationship with me for 21 years? and why? It is a very long time. He betrayed and told lies (during the relation I didn't know them), he played the hot-cold game constantly, he was a great lover, then a terrible one etc.
Most of the time, our friends adviced me to leave him, but I believed in him and the connection we had. Finally, he left me and said he was in love with someone else. Life is a big fat joke. I hate missing him.
I need any ideas about his staying with me for so long... .Thanks.

[clytie]

Oh, help! I have written this post under the wrong title  How can I move it to the "relationship ended- breakup crises" part?

[StanD]

Same here. I’ve been married to undiagnosed BPD SO for 23 years and I’m just now beginning to learn that my Caretaking tendencies are contributing to the prolonging of the issues and probably the only reason the relationship has continued this long. These Caretaker tendencies are probably low self esteem related. My feeling now is the more strong boundaries I create and communicate will cause greater conflict and lead to either changes on SOs part or my needing to make decisions about what I will continue to tolerate. I feel changes are necessary to remain my sanity,
.

Had you changed your behavior toward your SO which led them to decide he didn’t want to continue the relationship?

[clytie]

Yes, there were some changes. The biggest chance was we had a son. He was colic and didnt sleep at nights for about a year. I believe that he became a blue father. I became a crazy mum who tried to survive. Then when our son was 4, he was diagnosed with a rare illness and stayed at hospital for 5 days. And he is still under rhamotholigical tests every 3 months. My BPD ex told me that his affair with the OW started on the phone when we were at the hospital. They met on instagram. She is 7 years older than him. He said  the OW "healed his wounds, nurture his existence." He said I was a terrible woman after having a child. He felt so lonely and lost. And he believed that our son's illness was my fault.
I was the one who took care of everything and everyone. I looked after a child without any sleep or support, i did the housework, i did cooking, and at the hospital i was all alone. He was just sitting in the corridor with his phone (he was just talking to the OW and getting support).
I supported him all through my life. -but of course he thought i was never good enough- When I needed support, he decided I was a bad woman and replaced me.
While and after leaving, he was very cruel to me with no feelings. But, he called me once and said he wanted to go, but he felt like it was impossible to leave me completely. and asked me "should i kill myself to solve this?". Then he was so angry.