Indented vertical line on my forehead, spreading into more lines. Please help! I have an idea but hoping I'm wrong (Photo)

Hello everyone! So, I have had a line starting from my scalp down to my left eyebrow for over a year now. It was pretty subtle at first, I never thought much of it.. I'm tense a lot and suffer from headaches so i figured it could be from straining my forehead (tension). However, over the past few months it has gotten noticeably worse. Now it's fairly "deep", along with spreading across my forehead. It seems it's almost turning into a "W". It's definitely indented.. What is this?