Going nuts. Mature hairline or receding?

[Paranoid cow]

Hi there. I'm really new to all of this. I've never been bothered about my hair, I've always had quite thick hair but now for some reason I'm preoccupied with my hairline and worrying I'm going bald? My hairline is curved and not straight, but some people have told me my hair looks normal and I'm just maturing?

What do you guys think? I'm 21. Any responses would be greatly appreciated!

I have attached some photos of my current hair. The photo with a shorter beard and better resolution is of me about five years ago, just as a comparison.

[Paranoid cow]

Top of my head.