I need to know if my iPhone has been hacked

By hack, if you mean a stranger is remotely controlling or monitoring your device, then...

Keep the iPhone updated to the latest iOS always and never Jailbreak. That's it.

iOS / iPadOS devices cannot be hacked or infected with Virus / Malware / Spyware if it is updated to the latest iOS/iPadOS unless you have intentionally downloaded spurious software or unauthorized apps directly from the internet and installed them on your device or/and have Jailbroken. 

It (Hacking) also depends on how careful are you in sharing sensitive and valuable information pertaining to your iPhone such as Passcode, Password, etc with your friends and family members.

Be careful when sharing the device's sensitive and valuable information with friends and family members.

Thumb Rules:

1. Enable  Guided Access before handing over an iPhone to kids or to a stranger.
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device and payment methods
5. Beware of Phishing
6. Do not share your location with a stranger --> Find friends and share your location with Find My
7. Do not leave your iPhone unlocked and unattended in public places like offices, schools, malls etc.
8. If you see this --> What to do if you get an alert that an AirTag, Find My network accessory or set of AirPods is with you

Hello ~ What would lead you to think your iPhone may be hacked? Give us as many pertinent details as possible but never include your personal information here. Take a look at these very helpful articles by clicking on the links below…

Recognize and avoid phishing messages, phony support calls ...

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

Keeping your iPhone updated is one of the ways to keep your iPhone secure. Also never share your Apple ID or passwords. Post back with more details if you need further assistance. You may also contact Apple Support by going to lower left and clicking on Support or here…

Contact Apple for support and service

Hope this information helps.

~Katana-San~