Why is only one side of my hairline receding ?

It is common to see hair loss presenting asymmetrically where one side is worse than the other.  Hair loss is determined mostly by family history.  If you are concerned about hair loss then measures such as medical therapy should be taken to help slow down the loss.    

Thank you for your question, This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

Balding is not symmetrical and usually the right side balds more than the left (at least initially). A 2016 study of 41 men with early frontal balding showed that the right sidje was more recessed on average than the left. In fact,  the right side had a 23 % larger area of recession compared to the left side.In conclusion male balding is not symmetrical at first. See an expert for guidance on next steps to take.ReferenceAsymmetry of the Receding Hairline in Men With Early Androgenetic Alopecia.Azar RP, et al. J Cutan Med Surg. 2016.

Hair loss is often asymmetric in the hairline at first, and more commonly it starts on the right side.  As the years go by it does balance out.  You are in the early stages of hair loss; now would be a good time to start a maintenance program that includes finasteride (Propecia), laser therapy (LLLT), minoxidil (Rogaine) and/or platelet-rich plasma.  Go see a local hair restoration surgeon and come up with a plan that works for you. 

Hairline recession does not occur symmetrically. It is very common for one side hair loss to progress faster than the other side. When performing hair transplant we do take this into consideration and correct the hairline to be symmetric again.

Unfortunately hair loss never seems to be symmetrical. There is no rhyme or reason to how one loses hair. You appear to be forming a mature hairline but it’s impossible to know for sure if the other side will catch up.

asymmetrical hair loss is not uncommon in genetic balding. IF you wait long enough, the side that is not receding will catch up with the receding side unless you are aggressive in treating it medically