Hairline is intact but thin hair above hairline. Am I balding or just thinner hair in one spot? (photo)

  I am assuming you are in your early twenties,
it would be helpful if you could find a photo of your biological father around
the same age and take a look at his hair. 
This will give you an idea of what to expect now and in the future.  You appear to have the start of male pattern
balding.  You should see a hair
transplant specialist for an examination which includes a microscopic
evaluation.  This study will show if you
have miniaturization of the hair in the front compared to other areas of your
scalp.  More importantly, there are
medications available that can slow down the loss if it is indeed male pattern
balding.   Therefore, it is important to
get a diagnosis and go forward from there.

From the picture, you appear to be in the early stages of male pattern balding. Depending upon your age, drug like finasteride might stop it or possibly reverse it. Hair Transplantation will work nicely to fill in the area but taking the drug along with the surgery will stop you from developing shock loss