HELP how can I get rid of someone who has hacked my computer

If you believe your Apple Account has been compromised, then review the information here:

If you think your Apple Account has been compromised - Apple Support

Beyond that you will need to provide more information on what you are seeing and what happened last week, or possibly provide screenshots as long as they do not reveal any personal information.

Immediate steps ...

• If you believe your credit or debit cards have been taken over, report it to your bank(s) immediately. They will cancel the cards and issue new ones with new numbers. You can also review any fraudulent transactions and have them removed.
• Freeze your credit reports with all three agencies: Experian, TransUnion, Equifax. You can do this online with each. Don't just do a fraud alert, do a freeze. Fraud alerts do not prevent opening new credit; freezes do.
• Report the identity theft & and any fraudulent accounts and transactions to your local police. You may need a police report in order to pursue further actions.

Then ...

• Follow the advice given by @Mac Jim ID to recover your Apple Account.
• Report the problem to Amazon 1) to protect your own account if you have one and 2) to alert them to the fraudulent account that was created in your name.
• Report the problem to any other vendors where you believe a false account has been created or your own account has been taken over.

Consider reporting the identity theft to:

• Your state's Attorney General Office/Bureau of Consumer Protection
• The Federal Trade Commission at identitytheft.gov

If it becomes necessary, file an Identity Theft Affidavit (Form 14039) with the Internal Revenue Service