Hacked account and account name changed

Hello,

I was verifying my minecraft account on a discord server, and I have realised they hacked it. They have changed my account name ( I know they have not deleted it, because my friend said that my hacked account is online) and they also changed my password. The only info I have is the new minecraft username (they changed it too) and the previous name of the account and it´s password. I luckily have access to my email. This account is important to me and is my main account, so if anyone has any info or any guidance please let me know. All help is highly appreciated. 

Thanks.