Is there a way that I can stop my ex getting my info

To keep your Apple ID account secure, see the following Apple articles: 

If you think your Apple ID has been compromised

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

See who has access to your device or accounts

See who has access to your iPhone or iPad – Apple Support (UK)

Delete suspicious content from your devices

Delete suspicious content from your devices – Apple Support (UK)

Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to find where you're signed in - Apple Support

• if you see devices that don't belong to you, delete from your account.

Personal Safety User Guide -> Personal Safety User Guide – Apple Support (UK)

Manage and use your Apple ID -> Manage and use your Apple ID – Apple Support (UK)

(if you haven't already done this) Two-factor authentication for Apple ID -> Two-factor authentication for Apple ID - Apple Support

Change your Apple ID password -> Change your Apple ID password - Apple Support

• Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. 
• Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support

Never jailbroken your iPhone.

Yes. Make sure you are using your own Apple Account (ID) and do not share the log-in information. This document explains how to create a new Apple ID (create an Apple Account) --> How to create a new Apple ID - Apple Support

If you are using your own account, change the password. Exactly how you change your password depends upon if this is an adult or a child, and the equipment you have. Click on this link to learn how to change your Apple ID password --> Change your Apple ID password - Apple Support or Change your Apple ID password - Apple Support (video enhanced version)

Change your Apple ID password on your iPhone, iPad, iPod touch, or Apple Watch

1. Tap Settings > your name > Password & Security.

2 Tap Change Password.

3. Enter your current password or device passcode, then enter a new password and confirm the new password.

Forgot your password? Go to --> If you forgot your Apple ID password - Apple Support

4. Tap Change or Change Password.