Does propecia stop working?

[Eric5]

So I've been on propecia for about 6 consecutive months now and for the first three it was complete hell! I was losing a lot of hairs and it was just awful. I stuck it out though and by month 4 it all stopped and my hair was regrowing and everything was just magical. All the sudden now I'm starting to lose hair again and I'm losing all my smaller hairs that I regrew and then some. it's going on month 7. Am I just going through another shedding phase or has propecia just lost its magic for me?! I am very frustrated and concerned, if someone who has gone through something similar to this could help me out I would very much appreciate it.
Thank you, Eric