How do I (22F) be okay with my partner (21M) watching porn?

Hello, Im 22F with 21M been togetehr for 2 years. I’m wondering if anyone has any advice on how to start being more comfortable with my partner watching porn?

I think a big reason why I feel so insecure about it is because we’ve had some issues with our sex life, and he’s always told me it’s just because he has a low sex drive, but then he’d continue to watch porn which would make it feel like he’d rather wank to porn than sleep with me which was obviously hurtful. And he kept lying to me about watching porn which didn’t help because the lying also damaged my trust a bit.

However our sex life has got a bit better in the past month but now but I still can’t help but still feel upset and insecure over the porn. I’ve told him he can obviously do whatever he wants but please just to stop lying to me. I don’t want this to ruin our relationship, and I’m sick of it causing so much overthinking and insecurity on my end.

To me, I just can’t help but feel like, if he’s getting off to a girl, then surely he would want to sleep with her if he got the chance? Or I worry that he’s comparing me to the girls he watches. Maybe I’m deeping it too much I don’t know, but I just want to be get over this.

I’m just wondering is there anyone who’s actually been in a similar situation and managed to get over it? I really don’t want this to ruin our relationship and just wondered if anyone has some advice.

Thank you

TL;DR : partner watches porn and it makes me feel insecure, any advice on how to not feel insecure over it?