Look at your old school photos. If you see a noticeable difference in your hairline, then it's most definitely receding. I have a friend who has a similar hairline to that and his dad also has the same hairline with no hair loss at all so its possible you have just developed that as you've grown...
Best thing to do is take a photo of your hairline every 6 months and compare the results. I wouldn't start finasteride until you're certain because at this point I hardly see anything wrong with your hairline. Check your hairline for miniaturization and your scalp for a bald spot or diffuse thinning.
I'm 15 and mines similar to yours. It does suck looking around and seeing everyone with straight hairlines. :(
Anyway, you can try minoxidil now and take finasteride when you're 18 but besides that, there's nothing you can do.
You look around a NW2. If it makes you feel any better, I'm 15 and have a worse hairline so I guess the prime of my life is already ****ed. Good luck with finasteride and minoxidil mate!
Also, if you get diffuse thinning or a bald patch , look up about hair concealers. Since you have black hair...