Bf lying to me

My bf has now lied about his own bday date, like on the day, because he "doesn't like birthdays" we talked that out and he apologized for lying. Now he lied to me about him watching porn. I saw he looked up porn on his phone and later we got on the topic and he said he doesn't watch porn anymore. I said "i can tell when you're lying." i didn't tell him I actually saw it on his phone tho. And he kept denying it and said "I never lie to you." Well that was a lie in itself! I told him to please stop lying to me and he has the audacity to say "Lie about what? I don't lie." What do I do? I feel like I can't trust him and it's making me not feel as loving towards him. We've been living together for half a year and him lying at this point is a problem. I honestly don't think he would ever cheat on me, that would be worst case scenario, but these small lies I feel are disrespectful in themselves.