You have to create a new account on a new server then use the account migration tool. It’s not perfect; you’ll keep your followers but I think your posts won’t transfer over. Notes from the tool:

Before proceeding, please read these notes carefully:

• This action will move all followers from the current account to the new account
• Your current account’s profile will be updated with a redirect notice and be excluded from searches
• No other data will be moved automatically
• The new account must first be configured to back-reference this one
• After moving there is a waiting period during which you will not be able to move again
• Your current account will not be fully usable afterwards. However, you will have access to data export as well as re-activation.