My (F-20) and my boyfriend (M-20) lied to me for straight 6 months

Hello, I F (19) have been in a relationship with M (19) For 6 months now, a little over that tbh, he has always been a lovely boy, I love him a lot like genuinely

I have met him mom and his best friend (m) and everything and we are in a Long distance relationship and we met through hinge ( I know sounds ridiculous, but are very loyal to each other)

Last night, we were on a call and he confessed to me that his female best friend ( after we started dating they have not been meeting that frequently) and he was about to get into a FWB kind of relationship, it all started when he had a huge fight with his dad and he called her up and she proposed that idea to him, that time his 2 months old situationship had also ended so he was in more vulnerable state.

Note- this was all before he and I even met

I am honestly okay with all this, since it’s in the past and all but what’s bothering me is that for past 6 months I KEPT asking him if there was anything between you and her and he kept denying it although in the back of my mind I had an idea but he convinced me there was nothing

Since past 1 and half day it’s been bothering me so damn much, that how can he just lie blatantly on my face, on calls all the time, I feel like I can’t trust him for while atleast, right now he’s here back in the city and we are meeting and hanging out and today is our last meet up and tomorrow is his flight, i just don’t know how to behave honestly, I am not feeling that it anymore, I feel like crying constantly and I am just sad

What do I do? How do I deal with this?