My 2cents on this...
Im guna be honest here with you. That picture where you say your hair is thick is not. Its not thin but it aint thick. Theres thinning in the middle of your hairline, bit at the temples and your hair is dry and fluffled up aswell as being blonde which gives illusion of thickness. If you had your hair dyed black and shaved it, then i would be sure there would have been evident thinning. Unfortunately for you i think this is just a classic case of diffuse balding that has kicked into over drive. plus probably a shed from the propecia. Getting of it in my eyes is a mistake. The answer to your hair is simple....ROGAINE.
You might not like that but diffuse losers from what ive seen in here go quick once they notice hairloss. Its the % density thing. All seems fine until you pass that golden point and then scalp just keeps apeearing stornger and stronger. Personally i think rogaine would do wonders for you. It seems to be the holy grial for alot of diffuse thinners. Mj9 and SE freak are testament to that.
I also might add you have the luxury of having a rounded face and head and would look good with a shaved head as you apply this stuff twice a day.
I would give the meds the proper time and rogaine IS for you. Dont be so scared of it. It really isnt that bad. If propecia freaks you out so much try dutasteride or cut down on your dosage.
Believing you dont have hair loss is worst thing you can do. You DO HAVE diffuse thinning. Your pictures are a classic example.
May the luck of the irish be with you my friend.