Drugs like finasteride(Proscar) and dutasteride(Avodart) can also synchronize the hair shed cycles and this results in sheds. If you ride the shed out, the hair will come back in a few months, most likely thicker, but it will come back at the same thickness it was before at least I'd imagine. And if it doesn't, well the hair was on its way out anyway and the drug just isn't strong enough to stop that hair from miniaturizing. Follicles are funny things.
Stopping the drug now though would be the worst thing that you could do, because if my first possible explanation is true and that your hair shed because of the drug, by stopping it, within a week your DHT levels will be back up to what they were before starting, and that hair might grow in thinner, or perhaps thin so much that you can't even see it anymore. It's just gone. So I hope you aren't considering stopping now, for your sake.
And one thing to point out:
From looking at your before pic, and then looking at the after and where you're shedding from, I see that the hair from your "shedding" region was thin in comparison to the rest of your hair even before Proscar. Your one month pic looks like the same style of diffuse thinning that I had, and I recovered great from my 2-3 sheds that I endured all this time on dutasteride.