Ex boyfriend drama😴😬

So me and my ex boyfriend broke up a few weeks ago I believe and we broke up because he was always busy and had practise so I understood and everything and we talked about it, and then out of no where he Snapchats me saying don’t act nice and then talk shit about me behind my back don’t look at me or like get near me and so on. I was completely confused because I had not been saying anything negative about him especially because I knew he was facing some problems with depression and wanting to commit suicide. I’ve been talking to him best friend just as friends tho and we play fortnite together and whatever and I asked him to find our what I said because I still do not know what I said and apparently one of my best friends said I was talking shit to him but he denied it but his best friend still hasn’t told me what exactly my friend said to my ex. Now my ex is purposely trying to make me mad and I don’t know what to do can anyone help??