Boyfriend talking to ex

His ex hit him up after many yrs, after she left him for dead. Never talked to him again. But out of no where messages him.

He had the need to ask her questions about why she did what she did, I had a problem with it and definitely expressed myself to him, but now I’m finally calm about the situation and understood why. they had their conversation... He only shows me part of what he’s said to her, and tells me that’s the last thing he sent to her but in reality it wasn’t. Im upset about that because I felt like I deserved to be told the truth, but then again I don’t know if I’m invading his privacy. Am I right for being upset or should I give him his privacy? I’ve always told him to keep it 100% real with me, and as long as you don’t do anything wrong I won’t be upset with you but I just feel as if he’s hiding something. I don’t know. 😩😩 why lie to me??