Dating

Should I tell her again?

So my ex has messaged me again, he was sending sexual "pegging" memes to me honestly didn't know there was such a thing. It couldn't of been a worse time cause I was under the influence of alcohol. So I was stupid and responded back. He has a thing for "pegging" if you don't know what it is ill let you look it up for yourselves lol. I told him while we were in a relationship (over 2 years ago) I would try it. Because at the time I was interested in it. We didn't end up doing it. My friends and I needed a ride and I thought it was okay to ask him for one. He didn't come which was the best, I was an idiot I should've never asked for it. He said he wouldn't feel right doing it, but he thinks it's okay to message me? Lol. Anyway, I basically told him to be loyal to her. But he's done this before, thus is the second time of him doing this, I sent her screenshots the first time he did this. She went on vacation that day. I feel really bad for her, because in my eyes this is cheating big time. On the side note she did stay with him, when she should've left him the first time he did it. I need advice, please help.
Should I tell her again?
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