Is my iPhone hacked the square text?

Appearently people received a few mean messages from my number/phone and I never sent those. It happened yesterday. I looked online and it said if I got a text with square in it it could be hacked. I looked
And the day before yesterday I got a text saying "k (square)" it had an actual square in the message. It says only a square In it but It also had k in it. Is it hacked?

Do you have emoji 2? If someone does and sends you a emoji that you don't have it comes up as a square to it would have been a "k. " or something, the texts could be somone who just took your phone like a sister or brother or friend