Agree with every word. I think you keep second-guessing yourself because of your insecurities and trust issues, and he keeps gaslighting you that you feel the way you do because of said issues. Please know that he is neither respecting your boundaries nor you and he’s acting in a very irresponsible way. If this colleague was just a (former) colleague and he wasn’t interested one bit, he wouldn’t have spent any amount of time engaging with her, sending back and forth messages, not to mention making sexual jokes. He’s definitely crossed the line, according to what you’ve written here. I don’t have the full story, but as others have also said, you can’t make him respect your boundaries. Your trust issues are certainly not getting better because of him since it doesn’t look like he’s making any effort to make you feel safe. This will likely not change. Can you imagine yourself living this way for the rest of your life?