Just found out husband cheated (we have a 2 year old)

What should I do? He sent me this message and I’m not sure if it makes any sense what he said..or if I’m just too angry to understand anything right now? Please help

What questions should I ask? I really want to believe it was just phone sex..but he keeps acting defensive whenever I bring this issue up..like whaaaat?!?? I didn’t do anything you did idiot!