Hey simple. My hair loss is very similar to yours. At age 20 (almost 21) I noticed my hairline receded (mature hairline had formed). My hairline stayed put after that, BUT i began diffuse thinning on top at age 23. It caught me off guard because I was not familiar with Diffuse male pattern baldness, I thought all male pattern baldness involved receding temples + balding crown!
What guard are you using on your haircut?
Because I think as of right now it is barely noticeable. Honestly, to me it looks as though you're someone who has thin hair. I'm not saying you do not have male pattern baldness, you know your hair and changes to it better than anyone else. I'm just saying you're in good shape and the Telogen Effluvium sheds that propecia is going to cause a few months down the road shouldn't dramatically alter your hairs appearance (maybe go 1 size smaller if you feel uncomfortable during the sheds). Stick with your regimen for a full year. Some say they have even better results by the 2nd year. Good luck man.