Bro, I was about to ask the same question about my hair, then I saw yours and I don't have to anymore because yours looks exactly like mine. I'm same age basically too, 19, and mine started a year ago. Literally my hair looks fine looking back at pictures, then in a few months I noticed in a picture of me how bad it was, it happened so quickly. Then recently found out I have hypothyroidism and most likely autoimmune disease. I went to an endocrinologist today for my thyroid and she looked at my hair and said, oh that's Alopecia, not male pattern baldness. Alopecia and hypothyroidism are both autoimmune dieseases, and having one increases your chance of having the other. Also I guess just having hypothyroidism, aswell as low iron, could also be contributing aswell. She said I should see a dermatologist, they can reduce the inflammation. Then again, I don't know if endocrinologists are experts when it comes to hair loss, but thats what she told me. People on here might say differently. Also, did you have any hair loss anywhere else? I also had a streak down the center of my head when wet where there was barely any hair, but it grew back, and also I feel like I have less hair above my ears now too... the weird thing is my hairline is further back at the middle, then further down at the sides, and then when you get to my temples, thats where it really goes far back, like yours. I also noticed it looks like yours is worse on one side? Thats how mine appears also. So yeah, I think it very well might be your thyroid, or Alopecia, if my endocrinologist is right, I might take a picture of my own and post it.
Edit: This is mine... sorry if it seems like im trying to hijack your thread lol, im just trying to point out that its similar