Anonymous letter which shows that my boyfriend of three years is cheating on me. Should I ignore it?

To be honest it isn't going perfect between me and my boyfriend and I know I do sound jealous, but an ex of his decided to keep popping up in his life. He was very secretive about her and only told me that she pops up when she needs his help. A few months ago I started seeing more texts pop up on his phone. Each week he gotten more texts.

A few weeks ago I got fed up with her and he keeping her a secret. It was either me or her. He choose me and cut all ties with her which infuriated her. She even sended an angry text to him, which he showed me, where she was angry for unfriending her on Facebook.

Last week I got an anonymous letter with screenshots of texts between them and even texts to and from an other girl (which were very 18+). I literally got sick by reading them.

All these texts look like the screenshots were made from his point of view (on his phone). There was also a screenshot of texts between my boyfriend and me included, which I can confirm.

This all seems too real to be fake, but at the same time there is a rejected ex in play. As they say "Hell hath no fury like a woman scorned".
Anonymous letter which shows that my boyfriend of three years is cheating on me. Should I ignore it?
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