I would say it like this: I got my hair cut two weeks ago, but it was a big dissapointment. I feel I'm ugly with the new hairstyle. If I had known I would feel like this, I wouldn't have gotten my hair cut there. Hindsight is twenty-twenty, isn't it 😐 ? "Hindsight is twenty-twenty" is an idiom that means a person can see something clearly after it has already happened.

"I feel I LOOK ugly" or "it makes me look ugly" are natural phrases. Yes, hindsight is a wonderful thing - we definitely say this in British English ... and then go to a different hairdresser haha