How to get my iphone unhacked?

So my dad confronted me telling me he knew few people who could hack into my phone.well he said they showed him my text messages and i knew he wasn't lying cuz he knew what one of them said… Hes so low for this i can't trust him. Anyways does anyone know how i could possibly get my phone unhacked? Btw its an iphone5C i just got it too:'/ like wtf… I'm still in shock sorry…

Added (1). Turns out… He lied to me… Sorry and thank you to everyone who answered:/

Either figure out what program he used and uninstall it or do a factory reset. There are programs that can be sent via sms that can spy on you that may be difficut to remove.

Its not hacked, he's just reading your imessages as you both are using the same id.