Here is my story
I met guy A in 2008 and there was a possibility of us going out until he moved to another city. I really liked him but we lost contact after he left. About two months after he left I met guy B and he was from the same country as guy A. We hooked up, fell in love and we were together until 2011. I always felt he wasn't caring enough because his work and friends were more important than me. He never had tym for me, we discussed this and decided to break up and then he left the country. Early this year guy A comes back, we picked up from where we left off, I then find out him and guy B are friends from childhood. I told him about me and his friend, he had concerns at first but said he wants to be with me. He wanted a future with me but I told him that can't happen because I have a past with his friend Six months later guy B comes back, apologises and promises to change. I still love him and want to be with him but I don't want to tell him I slept with his friend as this will hurt him. I don't know if I should tell him what happened, if he forgives we get back to gether or should I keep quiet and me and guy A pretend nothing ever happened as he doesn't want his friend to know about us? I feel like a whore already but my heart is still with guy B. What should I do?

You broke up! He left! He left the country! That doesn't make you a whore. You were both 100% free to do what you want. I might say he doesn't need to know because you weren't 'cheating.' But he will probably find out from his friend. So yes, I would tell him.
If he can't handle this, then he's too selfish and egotistical. Who knows who he slept with?

He was not your boyfriend then so what difference does it make?
It certainly does not make you a whore. Would he be a dog if he slept with someone while you to were broke up?