Accused of cheating when I didn’t cheat

My ex just sent me a nasty ass paragraph saying I’m a cheater, disgusting, lying low life whore who’s bound to live a life of nothingness and I should be ashamed of myself. I didn’t even get the chance to reply whatsoever, I was immediately blocked on everything. Apparently I had sex with multiple other people and I’m lustful when that accusation is news to me. My ex and I have been broken up for 7 months but I still love them dearly and have tried to make an effort into coming back to their life but they always wanted space for themselves, if I did cheat I would of expected this to come but now that they’re accusing me of cheating I have no idea what to do.