my (22f) boyfriend (26m) is going to leave me because he thinks i'm masturbating in call. what do i even say?

i’m 22f, he’s 26m, we’ve been together almost 2 years long distance.

last night we were on a call watching a movie and there was this awkward moment between us so we just stayed quiet for the rest of it. after the movie, he said he had to go to the bathroom, and i also muted at some point because i felt like i needed to use the toilet too.

he ended up being gone for like an hour. during that time i was literally just laying in bed scrolling and posting on reddit.

when he came back, he immediately said something like “enjoying yourself without me?” in a weird tone. i was confused and asked what he meant, and he just completely flipped.

he started accusing me of masturbating on call while he was gone, saying i had my phone close to me and that he heard “wet/sloshing noises.” this is not the first time he’s thought this and asked me if i was doing it, and every time i’ve told him no, i’m not doing anything. he seems to think i'm some sort of extreme compulsive masturbator.

he was being extremely aggressive about it. calling me a liar over and over, saying he’s disgusted, threatening to block me, accusing me of sending nudes to someone else. i tried to explain i was literally just on reddit and even showed him what i was doing, but he didn’t care. he didn't care that a big part of who i am, and he knows this, that i am NOT a liar.

when i got upset and started freaking out (because he was about to block me), he said he could “hear the guilt in my voice.” no matter what i said, he just kept saying “stop lying.”

he also brought up other times where he claims he heard those sounds, including when i was “pretending to sleep” (i was actually asleep). he even said i’m “sick in the head” for how much i supposedly masturbate, which isn’t even true.

i tried to reason with him logically, but he already decided what he believes. he even said those sounds don’t happen when we’re actually doing anything sexual together on call, which makes no sense.

we ended the call with me asking him not to block me and to just wait until today to talk.

i genuinely don’t know what to say to him. i didn’t do anything he’s accusing me of, and i feel like nothing i say will change his mind. i don't want him to break up with me.

tldr:
my long-distance boyfriend accused me of masturbating and cheating on him during a call when i was literally just on my phone. he’s completely convinced i’m lying no matter what i say and even used my reaction as “proof.” we’re talking again today and i don’t know how to deal with someone who already made up their own version of events.