Unavailable Feelings

I have feelings for my married coworker. These are not feelings I want to have. When I see him I have feelings like guilt, inferiority, disappointment, and sadness. I have thoughts like “I’m not good/pretty/smart enough”, “He doesn’t choose me and why should he”, “I’m such an idiot for having feelings for him” and other thoughts that line up with those more or less. We work in a small office, in the same room together and I feel like the phyiscal proximity makes it worse because I feel like I don’t have “time” to get over it before I have to see him again. He has told me that he has feelings for me and that causes me to think other thoughts such as “He’s not genuine”, “It would never work”, “He’s a bad person for leading me on”. Nothing physical has happened and I won’t let it happen but I also don’t want to have all these thoughts and feelings. I feel like I’m not trusting in myself and I have low self esteem and that I deserve better. I realize all of those are thoughts too. I have tried to feel the feelings but I want to change them. I have tried to change my model, and this works for a short amount of time but I must not really believe the new models I’m making because it’s not sticking. I appreciate the help with my silly childish problem.