Little white lies! I need advice!

Ever since my boyfriend and I got to together he has made up little lies on the topic of sex. For example, I’m completely okay with him watching porn, however he would go out of his way to say ‘I don’t watch it anymore now I’m with you, it feels wrong.’ He would say this on multiple occasions, without me even bringing the topic up. However, he was showing me something on his phone and it came up in his recent searches.

Further down the line he’s lied about how his past relationships ended or why they ended. This turned into a huge discussion. I told him he doesn’t need to make up lies, just be honest, even if it’s embarrassing. He agreed he would stop. However, he started lying about him masturbating. I made a joke about he’s masturbating too much, that’s why we’re not having sex. He replied with ‘I don’t, I only do it if you send me pictures,’ however I don’t send pictures anymore.

I then jokingly brought it up again to see what he would say where he answer completely changed and said ‘it’s been ages like 5 days since I done it last.’

Why is he lying about things like this??

Any advice would be greatly appreciate