The original hair of one's teens without any loss whatsoever (not even the mature hairline) is NW1. And, given your age (30's?) it's highly unlikely that you were a NW1 before you started Propecia. I have seen VERY few 30+ year olds (most sites say 4% of mature men are NW1, I'd say more like 1% based on my own observations) who have not receded AT ALL since they were 17. Recession can be so little that its difficult to tell one has receded even on close observation with hair pulled back. So you were very likely a NW2 or so before you started Propecia.
And yes , it is quite possible , although very uncommon, to go from NW1 to NW3 in 3 months (I know one guy who went from NW1 to almost NW5 in less than a year - the worst part is that he's just 18. But don't get scared by this - this case is an example of a rare, early and severe form of male pattern baldness which is always accompanied by strong family history of such baldness, often starts well before age 20 and usually progresses rapidly to NW7. You are VERY VERY unlikely to have this form of male pattern baldness.)
You have said in earlier posts that you saw no miniaturization at all at the area where you are receding - normal, thick hairs just fell out and nothing came to replace them. If this is ONLY male pattern baldness and nothing else, it is indeed very unusual , but not unthinkable. It is possible (as others on this site have also stated) , that the miniaturization of those temple follicles occurred so quickly that each follicle probably went through all of the shorter growth cycles in a day or less. But that's very unlikely. Has anybody on either side of the family lost their hairline so quickly at around your age? Now, because the loss is occurring at an male pattern baldness-prone area (temporal hairline) ,one of the problems causing this rapid loss is undoubtedly male pattern baldness. But male pattern baldness alone should not be making you lose your hair so fast, without even seeing any thinning in the meantime. It MAY be Telogen Effluvium (telogen effluvium) severely aggravating male pattern baldness . But remember, that if it is Telogen Effluvium, no matter how severe, the hair will grow back (well, whatever hair which has'nt succumbed to male pattern baldness while the Telogen Effluvium is going on, anyway)
Is the receding still continuing rapidly? Has'nt it slowed down atleast a little? Go to a good derm FAST, because you need a proper diagnosis, and if at all it is severe male pattern baldness (god forbid) the hair may never return. DON'T wait to lose more hair , because you don't know what is making you lose it - Telogen Effluvium in conjunction with "typical" male pattern baldness, or just plain severe male pattern baldness.
Go to the derm and find out fast.
Best of luck,
Arjun
