[BA156]

Hello.
I am 18. I am fine with the size of my penis and so is my girlfriend, this is not the problem I have my problem is that I appear to have shrunk over the past 2 years. I used to be about 8" and now I am 6", I am fine with this as more positions are now available but I don't want to continue shrinking. Is there any medical reason for this, perhaps something vascular?
I have gained a few stone over the past 2 years as well but am still in the "normal" range on my BMI. I am not especially healthy but I am not unhealthy either.
I also have marks on my inner thighs that resemble stretch marks that may be related but I'm not sure.
Thanks in advance for any response.
B x