I wanna hear y’all’s opinions on this!!!

I’m new to Reddit, and don’t post often but I remembered a situation with my ex that still baffles me years later. So me and my ex boyfriend were together for almost 4 years. At the start of our relationship (on my BIRTHDAY, mind you) he went to stay with his ex because he was “still really close with her little sister”. My stupid ass believed that. While he’s there, he tells me that he slept on the couch in a separate room than everyone else. Fast forward about 6 months, we were on the way to have dinner with his mom, and I had a weird feeling about the situation so I asked again. He proceeds to tell me that him and his ex slept in the same bed (a twin bed) but didn’t do anything. I obviously broke down, and that’s when he realized that he lied to me about sleeping on the couch previously. After this whole ordeal, he argued that it wasn’t considered cheating because “they didn’t even touch”. He made me feel clinically insane over this. I am far over it now I just wanted some outside opinions, was that cheating? Even if they didn’t touch? Btw he did have the option to sleep on the couch, he chose to share a bed with his ex.