I had not seen someone in over 15 years and he said let me in, trust me, and I won't hurt you. He still was seeing someone and I said I needed more. He dumped me. I have know this person for a long time. Now for the last several days, all I do is cry. It hurt so much. He won't talk to me or email me because my email came out confrontational.
If you had not been in a relationship for many years, and you finally trusted someone, then this sort of behaviour is likely to hit you hard.
Maybe he really believed that he wouldn't hurt you, but he did.
Perhaps , once he had started seeing you, he concluded that you were not right for each other after all.
Or maybe he just set himself the challenge of getting you to let him into your life, and, once the challenge was over, the relationship was over.
The fact that he was seeing someone else rather indicates that he wasn't too worried about hurting either you or his girlfriend ~ perhaps you were wrong to trust him, but maybe you trusted him because you knew him and he swept you off your feet ~ and, after so long, you were ready to be swept along.
I am sorry that this has happened, but it has been a learning experience for you ~ a negative one, unfortunately.
It's bound to hurt, and he has treated you badly and continues to treat you badly by ignoring your messages.
Personally, I think that you should not bother further with him. He has shown his true colours.
But you can take something positive from this ~ you have started dating again and so you can now find a decent man to spend time with.
Obviously, you may not want to 'seek a boyfriend', but you can seek out opportunities for meeting new people ~ a club, hobby, evening class, or something, where you can meet up with others who have similar interests. Just be careful to keep yourself safe.
Give yourself time to cry over this, but then start again. Don't let him ruin future relationships just because he treated you badly. He's not worth it.
Take care