I hate saying sorry

I started a new on may 8 and I really like it. My boss is awesome and so are my coworkers well except the one who bullies me. I asked my boss to check something out and he said I can’t right now I am working on project I will try to check it tomorrow. And before I realized it I said sorry. Than he gave me a much more serious tone. And than even though he didn’t get mad at me or anything I felt like I was stupid again and hated myself again. Why is it so hard for me to not say sorry.