17 and premature receding temples

I’m 17 and about a month ago, I noticed that my temples are thinning although it was with right side only although overtime seems like left side going in same path. I bought alecpin caffeine shampoo as caffeine was shown to stimulate hair growth in studies and ‘cancel out’ the effect of testosterone ( atleast thats what I read ) and it was really cheap too. I have been applying it every 2-3 days. It has grown lots of small hairs and I can see my juveline hairline with these small hairs ( they are colored black but not very thick so don’t think they are vellus hairs ). I want to thicken these hairs and make them grow more so I can get more thicker temples. I’m guessing the reason why I have seen lot of regrowth is because I caught my thinning temples at a very early stage. I really want to keep my hair as it is for atleast another 4 years and then maybe I could start using RU or whatever is best at the time. For now, can anyone please suggest what I should do or use to try and prevent my temples from getting any thinner. I don’t have much to spend every month so I can’t invest in stuff like regaine. I’d be willing to spend like £15 a month to try and keep my hair as it is today( would prefer if it is something I can buy from like boots or some local shop). Also, My brother is around 25 and he has lost some hair at the temples and he isnt thinning anywhere else and they are a bit like this so chances are im going in same path
http://img451.imageshack.us/img451/1613/davidbeckham025b15dzt1.jpg

Thanks

Anyone?

Could someone suggest some good topical treatment to stop hairloss at its tracks ? I want to use it at the temples where there are tiny hairs. Something without any major side effects.