Hi! My name is Aj and Im an Independent Advisor here to help! Im sorry to hear about your account. Please go to this link https://support.microsoft.com/en-us/account-billing/how-to-recover-a-hacked-or-compromised-microsoft-account-24ca907d-bcdf-a44b-4656-47f0cd89c245 and use the sign in helper tool. Also secure you account by changing the password, sign out everywhere, check and remove activities you are not familiar.
Submit the account recovery form at https://account.live.com/acsr and give as much info as you can: old passwords, services used like Xbox, Skype, etc., purchase info, etc. If you have proof of purchase of Minecraft (order receipts, transaction IDs, billing method) that helps a lot. You can submit upt to 2 forms a day. After submission kindly allow 24-72 hours for verification.
Also report it to Minecraft/Monjang's support
https://help.minecraft.net/hc/en-us/request/new?ticket_form_id=360001225811
Check this link https://help.minecraft.net/hc/en-us/articles/27202503868685-Troubleshooting-Locked-Compromised-or-Stolen-Microsoft-Accounts