My ex just texted me and asked me if I ever cheated on him.

When we broke up a few months earlier, I told him I cheated on him. I was mad that we broke up. Later on I said I didn’t. We just left it at that and never made it clear. I actually did cheat on him tho! I sucked another guys dick. But idk if I wanna tell him that. I don’t feel like he deserves the truth. Should I ?