Why did my boyfriend lie to me?

Anonymous
Last year I told my boyfriend that I am in debt $5,000 on my credit card and I didn’t think he would tell anyone but today I saw his phone that he was getting texts from his mom asking about how it’s going with me paying off my credit card and her saying "a person has to earn more money than they spend". He doesn’t know I saw the messages but then yesterday when I asked him it he ever mentioned it to his mom he said he never did and he was like “ oh that’s really personal, I wouldn’t do that to you.” and then he told me straight to my face "I would never lie to you about anything ". Now I don’t know how to feel because he obviously lied to me about this. And now I’m wondering if he lies to me about other things too. I'm not upset he told his mom because maybe he was just concerned about my situation and wanted to vent to his mom - I'm upset that he lied straight to my face. And when I told him that my ex use to lie to me he agreed that it's really disrespectful to lie to someone like that. And then he just kept saying "I'd never do that to you" Thoughts?
Why did my boyfriend lie to me?
5 Opinion