What would you advice me?

My fiancé cheated on me after an 8-year relationship with another girl

He left me for her for no other reason

He now lives with her

She doesn't know what happened at all

This happened a year ago

I was trying to get over it and recover and I was in a lot of pain because I felt that I was wronged

But a month ago my father passed away

And I felt that I needed my ex-boyfriend and I sent him messages via WhatsApp and his response was that he couldn't repeat the same mistake twice

And if that girl wasn't in his life, he would have been by my side

By chance his girlfriend saw the conversations between us

And she sent me a harsh message and asked me not to contact him again

Because I ruin their relationship

I want to understand

Is life always unfair?

Who is the wronged one here

And am I a bad person because I needed someone who held me up with hope all those years

What would you advice me?
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