Do I have a receding hairline? Could my hairline just be maturing? Will it stop moving once it's done moving back? (Photo)

This is a great topic and it is important to understanding there sometimes no absolute "yes" or "no" answers. Maturing hairlines and receding hairlines both have hairs that are converting from terminal to vellus hairs (ie "miniaturizing"). So if someone with a maturing hairline is told there are no miniaturized hairs seen it is rather meaningless unless a description is given where they are seen and not seen. The only way to change a hairline is to get rid of the hairs through miniaturization. The two processes can appear similar. It could be just maturation you are experiencing  - absolutely. But please don't  use miniaturization as your main guide but rather focus on the position where the hairlines is moving too. Your doctor needs photos from your past and a ruler. The only way to "mature" a hairline is to miniaturize these hairs and then convert them to vellus hairs. Men with hairline maturation show miniaturization of hairs. Men with AGA show miniaturization of hairs. It is simply that the miniaturization in pure "hairline maturation" does not extend far back. Evaluating hairline maturation vs balding (sometimes) is not easy in early stages. Previous photos and a ruler help determine the current position of the hairline vs the past. One can often only conclude "At the present time, there is a high chance what we are seeing only represents maturation of the hairline." 

Keep in mind that hair loss is progressive. It is important to get on a preventative regimen. You should switch to an organic shampoo. You can also consider a natural DHT blocker like Saw Palmetto. There are also medications like Finasteride (a DHT Blocker) and Minoxidil (Rogaine) that can be very helpful in maintaining you existing hair, helping to prevent future loss and even regrow some hair. Before taking any medications you should discuss this with your general physician.

That is the correct question to ask.  Your biggest enemy is the progressive
thinning leading to a balding pattern that is not evident at this point in
time. The degree of thinning that you are experiencing would suggest that
you should see a doctor who has a HAIRCHECK instrument and will most likely will get Bulk Measurements of your
hair to determine the degree of the thinning that you are presently
having. If the diagnosis is early genetic hair loss (the most common cause
of hair loss in young men), then the best treatment would be the drug finasteride
which is highly effective in men of your age and may not only stop the
hair loss but possibly reverse it. If you are developing a more advanced
balding pattern the best test to get will determine the Bulk Measurements
of your hair and this will show, over a one-year time frame, how effective
the treatment will be. Once you know this information, then you and your
doctor need to develop a MASTER PLAN which will define what you need to do
over the years to come.