I'm being accused of catfish in my ex boyfriend?

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This morning I got a message from my ex boyfriend saying 'I know all about your fake accounts, is this you?' And sends me a picture of this girl who had uploaded 3 hours ago, mind you, while I was asleep!! She looks the same in every single picture, so I find it hard for that to be fake because of all the same person in every picture. I could be wrong. 
He then says 'you know what I'm talking about you liar' and I'm really confused as to what he is talking about? 
I don't catfish, I don't have fake profiles or anything stupid like that. I don't understand how someone can be so stupid? 
And why am I getting the blame? Why can't you just believe it was someone else, it certainly wasn't me. None of them are. 
Now that was my rant, I have a few questions? 
How do I tell him none of the fake accounts are me? 
Now he will go tell the whole school, what am I supposed to do? Everyone will be live him. Wtf is going on.